Articles with a low-elastic modulus layer and retained strength

ABSTRACT

One or more aspects of the disclosure pertain to an article including a film disposed on a glass substrate, which may be strengthened, where the interface between the film and the glass substrate is modified, such that the article has an improved average flexural strength, and the film retains key functional properties for its application. Some key functional properties of the film include optical, electrical and/or mechanical properties. The bridging of a crack from one of the film or the glass substrate into the other of the film or the glass substrate can be suppressed by inserting a nanoporous crack mitigating layer between the glass substrate and the film.

CLAIM OF PRIORITY

This application is a continuation application that claims the benefitof priority under 35 U.S.C. § 120 of U.S. patent application Ser. No.17/038,508, filed Sep. 30, 2020, which is a divisional application thatclaims the benefit of priority under 35 U.S.C. § 121 of U.S. patentapplication Ser. No. 14/053,093, filed Oct. 14, 2013, now U.S. Pat. No.10,829,409, which claims the benefit of priority under 35 U.S.C. § 119of U.S. Provisional Application No. 61/712,908, filed on Oct. 12, 2012,and the benefit of priority under 35 U.S.C. § 119 of U.S. ProvisionalApplication No. 61/820,395, filed on May 7, 2013, the entire contents ofeach of these documents are hereby incorporated herein by reference forall purposes.

BACKGROUND

This disclosure relates to articles including a glass substrate that hasa film disposed on its surface, and a modified interface between thefilm and the glass substrate such that the glass substrate substantiallyretains its average flexural strength, and the film retains keyproperties for its application.

Articles including a glass substrate, which may be strengthened orstrong as described herein, have found wide usage recently as aprotective cover glass for displays, especially in touch-screenapplications, and there is a potential for its use in many otherapplications, such as automotive or architectural windows and glass forphotovoltaic systems. In many of these applications it can beadvantageous to apply a film to the glass substrates. Exemplary filmsinclude indium-tin-oxide (“ITO”) or other transparent conductive oxides(e.g., aluminum and gallium doped zinc oxides and fluorine doped tinoxide), hard films of various kinds (e.g., diamond-like carbon, Al₂O₃,AlN, AlO_(x)N_(y), Si₃N₄, SiO_(x)N_(y), SiAl_(x)O_(y)N_(z), TiN, TiC),IR or UV reflecting layers, conducting or semiconducting layers,electronics layers, thin-film-transistor layers, or anti-reflection(“AR”) films (e.g., SiO₂, Nb₂O₅ and TiO₂ layered structures). In manyinstances these films must necessarily be hard and/or have a highelastic modulus, or otherwise their other functional properties (e.g.,mechanical, durability, electrical conductivity, optical properties)will be degraded. In most cases these films are thin films, that is,they generally have a thickness in the range of 0.005 μm to 10 μm (e.g.,5 nm to 10,000 nm).

When a film is applied to a surface of a glass substrate, which may bestrengthened or characterized as strong, the average flexural strengthof the glass substrate may be reduced, for example, when evaluated usingball-drop or ring-on-ring strength testing. This behavior has beenmeasured to be independent of temperature effects (i.e., the behavior isnot caused by significant or measurable relaxation of surfacecompressive stress in the strengthened glass substrate due to anyheating). The reduction in average flexural strength is also apparentlyindependent of any glass surface damage or corrosion from processing,and is apparently an inherent mechanical attribute of the article, evenwhen thin films having a thickness in the range from about 5 nm to about10 μm are utilized in the article. Without being bound by theory, thisreduction in average flexural strength is believed to be associated witha low strain-to-failure of such films relative to the highstrain-to-failure of strengthened or strong glass substrates, togetherwith crack bridging between such a film and the glass substrate and, insome cases, an increase in the stress intensity factor at crack tipsassociated with high elastic modulus of the film and/or increased cracklength of cracks that are bridging between the film and the glasssubstrate. In view of this new understanding, there is a need to preventfilms from reducing the average flexural strength of glass substrates.

SUMMARY

One or more aspects of this disclosure pertains to an article includinga glass substrate, a crack mitigating layer disposed on the glasssubstrate and a film disposed on the crack mitigating layer. In one ormore embodiments, the crack mitigating layer is disposed on a firstmajor surface of the glass substrate, forming a first interface, and thefilm is disposed on the crack mitigating layer, forming a secondsubstrate. In one or more embodiments, a crack originating in the filmrequires a greater load to bridge across the second interface than theload required to bridge across the first interface. In otherembodiments, the stress intensity factor (K) of a crack originating inthe film is reduced as the crack bridges into one or more of the crackmitigating layer and the glass substrate. In some examples, the stressintensity factor is reduced by at least about 10%. In one or moreembodiments, the crack mitigating layer causes the difference in loadrequirement and/or the change in the stress intensity factor. In otherembodiments, the crack mitigating layer increases the load required forthe crack to bridge from the film into the glass substrate by at leastabout 10%.

The crack mitigating layer may cause a crack, which originates in eitherthe film or the glass substrate and enters into the crack mitigatinglayer, to remain within the crack mitigating layer. In one or moreembodiments, the crack mitigating layer effectively confines a crackoriginating in one of the film and glass substrates from propagatinginto the other of such film and glass substrate. In one option, thecrack mitigating layer causes the crack to propagate within the crackmitigating layer in a direction substantially parallel to the firstinterface and/or second interface. In one or more alternativeembodiments, the crack mitigating layer causes the crack to propagatesubstantially along either the first interface or the second interface.

In other embodiments, the film has an elastic modulus that is greaterthan the elastic modulus of the crack mitigating layer. The elasticmodulus of the crack mitigating layer may be about 50 GPa or less, inthe range from about 1 GPa to about 50 GPa or in the range from about 5GPa to about 40 GPa. The crack mitigating layer of some embodiments mayinclude a porous material or a nanoporous material. The crack mitigatinglayer may include a porosity in the range from about 10% by volume toabout 50% by volume. In some embodiments, the crack mitigating layer hasan average pore size of less than about 50 nm. The porous or nanoporousmaterial may include an inorganic material such as, for example, SiO,SiO_(x), SiO₂, Al₂O₃, AlN, AlO_(x)N_(y), Si₃N₄, SiO_(x)N_(y),SiAl_(x)O_(y)N_(z), TiO₂, Nb₂O₅, Ta₂O₅, ZrO₂, GeO₂, SiC_(x)N_(y),SiC_(x)O_(y)N_(z), SiC, Si, Ge, indium-tin-oxide, tin oxide, fluorinatedtin oxide, aluminum zinc oxide, and/or zinc oxide. In other embodiments,the crack mitigating layer, which may be porous or non-porous, mayinclude a polymeric material selected from one or more of polyimide,fluorinated polyimide, polyetherimide, or polyethersulfone. In one ormore specific embodiments, the crack mitigating layer includesnanoporous vapor-deposited inorganic SiO, SiO_(x), or SiO₂ having anelastic modulus in a range from about 5 GPa to about 40 GPa.

The crack mitigating layer may optionally exhibit an opticaltransmission haze of less than about 10%. In some embodiments, the crackmitigating layer may have a refractive index in a range from about 1.3to about 1.7. The crack mitigating layer of some embodiments may exhibita fracture toughness of about 1 MPa·m^(1/2) or less.

The film of one or more embodiments includes one or more functionalproperties, such as optical properties, electrical properties andmechanical properties. The functional property or properties of the filmare substantially retained after combination with the crack mitigatinglayer. In one variant, the film can include transparent conductive oxidelayers, IR reflecting layers, UV reflecting layers, conducting layers,semiconducting layers, electronics layers, thin film transistor layers,EMI shielding layers, anti-reflection layers, anti-glare layers,dirt-resistant layers, self-cleaning layers, scratch-resistant layers,barrier layers, passivation layers, hermetic layers, diffusion-blockinglayers, fingerprint-resistant layers and combinations thereof. The filmmay include Al₂O₃, AlN, AlO_(x)N_(y), Si₃N₄, SiO_(x)N_(y),SiAl_(x)O_(y)N_(z), TiO₂, Nb₂O₅, Ta₂O₅, ZrO₂, SiC_(x)N_(y),SiC_(x)O_(y)N_(z), SiC, indium-tin-oxide, tin oxide, fluorinated tinoxide, aluminum zinc oxide, and/or zinc oxide.

The film may be formed from a single layer or a plurality of layers. Thethickness of the film may be determined in relation to the thickness ofthe crack mitigating layer. In some embodiments, the thickness of thecrack mitigating layer may be less than or equal to about 3 times thethickness of the film. In other embodiments, the thicknesses of the filmand the crack mitigating layer may each be about 5 micrometers or less.

In one or more embodiments, the glass substrate includes opposing majorsurfaces and exhibits an average strain-to-failure that is greater thanthe average strain-to-failure of the film. For example, the glasssubstrate may exhibit an average strain-to-failure that is greater thanabout 0.5%. The glass substrate may be chemically strengthened and mayexhibit a compressive stress greater than about 500 MPa and acompressive stress depth-of-layer greater than about 15 μm.

In one or more embodiments, the article exhibits an average flexuralstrength that is substantially greater than the average flexuralstrength exhibited by articles that include the glass substrate and thefilm but no crack mitigating layer.

A second aspect of this disclosure pertains to a method of forming anarticle. In one or more embodiments, the method includes a glasssubstrate, disposing a porous crack mitigating layer on the glasssubstrate, disposing a film having one or more functional properties onthe crack mitigating layer, and controlling the porosity or the elasticmodulus of the crack mitigating layer. In one or more embodiments, themethod may include controlling the porosity or the elastic modulus ofthe crack mitigating layer to maintain the average flexural strength ofthe glass substrate and/or the functional properties of the film. Themethod includes forming the crack mitigating layer via vacuumdeposition. The method of one or more embodiments may includestrengthening the glass substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an article comprising a glass substrate, afilm and a crack mitigating layer, according to one or more embodiments.

FIG. 2 is a schematic diagram of the development of a crack in a filmand its possible bridging modes.

FIG. 3 is an illustration of the theoretical model for the presence of acrack in a film and its possible bridging as a function of elasticmismatch α.

FIG. 4 is a diagram illustrating the energy release ratio G_(d)/G_(p).

FIG. 5 is a graph presenting ring-on-ring load-to-failure performance ofglass substrates or articles according to Examples 1A-1J.

FIG. 6 is a probability plot of ball drop performance of glasssubstrates or articles according to Examples 2A-2D.

FIG. 7 is an illustration of an article according to Example 3A.

FIG. 8 is an illustration of an article according to Example 3B.

FIG. 9 is an illustration of an article according to Example 3C.

FIG. 10 is a modeled optical reflectance spectrum according toComparative Examples 4A and 4B.

FIG. 11 is a modeled optical reflectance spectrum according to Example4C and Example 4D.

FIG. 12 is a modeled optical reflectance spectrum according to Example4E and Comparative Example 4F.

FIG. 13 is a graph presenting ring-on-ring load-to-failure performanceof glass substrates or articles according to Examples 5A-5E.

FIG. 14 is a graph presenting ring-on-ring load-to-failure performanceof glass substrates or articles according to Examples 5A and 5F-5H.

FIG. 15 is a graph presenting ring-on-ring load-to-failure performanceof glass substrates or articles according to Examples 6A-6D.

FIG. 16 is a graph presenting ring-on-ring load-to-failure performanceof glass substrates or articles according to Examples 6A-6B and Examples6E-6F.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details may beset forth in order to provide a thorough understanding of embodiments ofthe disclosure. However, it will be clear to one skilled in the art whenembodiments of the disclosure may be practiced without some or all ofthese specific details. In other instances, well-known features orprocesses may not be described in detail so as not to unnecessarilyobscure the disclosure. In addition, like or identical referencenumerals may be used to identify common or similar elements.

Referring to FIG. 1, aspects of this disclosure include an article 100including a film 110 and a glass substrate 120 wherein the interfacialproperties between the film 110 and the glass substrate 120 are modifiedsuch that the article substantially retains its average flexuralstrength, and the film retains key functional properties for itsapplication. In one or more embodiments, the article exhibits functionalproperties that are also retained after such modification. Functionalproperties of the film and/or article may include optical properties,electrical properties and/or mechanical properties, such as hardness,elastic modulus, strain-to-failure, abrasion resistance, mechanicaldurability, coefficient of friction, electrical conductivity, electricalresistivity, electron mobility, electron or hole carrier doping, opticalrefractive index, density, opacity, transparency, reflectivity,absorptivity, transmissivity and the like.

In one or more embodiment, the modification to the film-glass substrateinterface includes preventing one or more cracks from bridging from oneof the film 110 or the glass substrate 120 into the other of the film110 or the glass substrate 120, while preserving other functionalproperties of the film 110 and/or the article. In one or more specificembodiments, as illustrated in FIG. 1, the modification of theinterfacial properties includes disposing a crack mitigating layer 130between the glass substrate 120 and the film 110.

The term “film”, as applied to the film 110 and/or other filmsincorporated into the article 100, includes one or more layers that areformed by any known method in the art, including discrete deposition orcontinuous deposition processes. Such layers may be in direct contactwith one another. The layers may be formed from the same material ormore than one different material. In one or more alternativeembodiments, such layers may have intervening layers of differentmaterials disposed therebetween. In one or more embodiments a film mayinclude one or more contiguous and uninterrupted layers and/or one ormore discontinuous and interrupted layers (i.e., a layer havingdifferent materials formed adjacent to one another).

As used herein, the term “dispose” includes coating, depositing and/orforming a material onto a surface using any known method in the art. Thedisposed material may constitute a layer or film as defined herein. Thephrase “disposed on” includes the instance of forming a material onto asurface such that the material is in direct contact with the surface andalso includes the instance where the material is formed on a surface,where one or more intervening material(s) is between the disposedmaterial and the surface. The intervening material(s) may constitute alayer or film, as defined herein.

As used herein, the term “average flexural strength” is intended torefer to the flexural strength of a glass-containing material (e.g., anarticle and/or a glass substrate), as tested through methods such asring-on-ring, ball-on-ring, or ball drop testing. The term “average”when used in connection with average flexural strength or any otherproperty is based on the mathematical average of measurements of suchproperty on at least 5 samples, at least 10 samples or at least 15samples or at least 20 samples. Average flexural strength may refer tothe scale parameter of two parameter Weibull statistics of failure loadunder ring-on-ring or ball-on-ring testing. This scale parameter is alsocalled the Weibull characteristic strength, at which a material'sfailure probability is 63.2%. More broadly, average flexural strengthmay also be defined by other tests such as a ball drop test, where theglass surface flexural strength is characterized by a ball drop heightthat can be tolerated without failure. Glass surface strength may alsobe tested in a device configuration, where an appliance or devicecontaining the glass-containing material (e.g., an article and/or aglass substrate) article is dropped in different orientations that maycreate a surface flexural stress. Average flexural strength may in somecases also incorporate the strength as tested by other methods known inthe art, such as 3-point bend or 4-point bend testing. In some cases,these test methods may be significantly influenced by the edge strengthof the article.

In one or more embodiments, the crack mitigating layer 130 prevents orsuppresses the bridging of one or more cracks originating in one of thefilm 110 or the glass substrate 120 into the other of the film 110 orthe glass substrate 120. In one or more specific embodiments, the crackmitigating layer 130 prevents crack bridging from one of the film 110 orthe glass substrate 120 into the other of the film 110 or the glasssubstrate 120 by causing an increase in the average strain-to-failure ofthe film 110. The crack mitigating layer 130 may increase the averagestrain-to-failure of the film 110 by reducing the stress that may beformed in the film 110 during formation or application on the glasssubstrate. In such embodiments, it is believed that the increase in theaverage strain-to-failure of the film 110 prevents cracks from bridgingfrom one of the film 110 or the glass substrate 120 into the other ofthe film 110 or the glass substrate 120. In other embodiments, the crackmitigating layer 130 does not change the strain-to-failure of the film110, that is, cracks still form in the film 110 under loading, but thebridging of these cracks between the glass substrate 120 and the film110 is prevented or suppressed by the crack mitigating layer 130. Inthese embodiments, the crack mitigating layer 130 may prevent the cracksin the film 110 from bridging to the glass substrate 120 through cracktip blunting, crack arrest, crack deflection, delamination, or otherrelated mechanisms, as will be further described below.

As used herein, the terms “bridge”, or “bridging”, refer to crack, flawor defect formation and such crack, flaw or defect's growth in sizeand/or propagation from one material, layer or film into anothermaterial, layer or film. For example, bridging includes the instancewhere a crack that is present in the film 110 propagates into anothermaterial, layer or film (e.g., the glass substrate 120). The terms“bridge” or “bridging” also include the instance where a crack crossesan interface between different materials, different layers and/ordifferent films. The materials, layers and/or films need not be indirect contact with one another for a crack to bridge between suchmaterials, layers and/or films. For example, the crack may bridge from afirst material into a second material, not in direct contact with thefirst material, by bridging through an intermediate material disposedbetween the first and second material. The same scenario may apply tolayers and films and combinations of materials, layers and films. In thearticles described herein, a crack may originate in one of the film 110or the glass substrate 120 and bridge into the other of the film 110 orthe glass substrate 120. As will be described herein, the crackmitigating layer 130 may prevent cracks from bridging between the film110 and the glass substrate 120, regardless of where (i.e., the film 110or the glass substrate 120) the crack originates.

The term “prevent”, when associated with prevention of crack bridging,refers to preventing crack bridging at one or more selected loadlevel(s) (or ranges of loads) or flexural state(s). This does not implythat crack bridging is prevented for all load levels or flexural states.Rather, this generally implies that crack bridging is prevented for aparticular load, stress, or strain level or range that would ordinarilycause crack bridging without the presence of the crack mitigating layer.

In one or more embodiments, the crack mitigating layer 130 may notprevent crack bridging between the film 110 and the glass substrate 120,but rather the crack mitigating layer may suppress the growth of cracksthat are bridging between the film 110 and the glass substrate 120,relative to an article without the crack mitigating layer. Accordingly,in one or more embodiments, there may be pre-existing cracks in one ofthe film 110 and/or the glass substrate 120 that bridge between the film110 and glass substrate 120, or cracks may form during the applicationof load/stress, but the growth of these cracks is suppressed by thepresence of the crack mitigating layer. As used herein, the term“suppress” when used in relation to crack growth includes delaying crackgrown at lower loads until a higher load is applied to the article atwhich point the crack grows. The term “suppress” also includes reducingcrack growth rate (or speed) at a given load or stress level applied tothe article.

In other embodiments, the crack mitigating layer 130 may form apreferred path of crack propagation other than bridging between the film110 and the glass substrate 120. In other words, the crack mitigatinglayer 130 may deflect a crack forming in one of the film 110 and theglass substrate 120 and propagating toward the other of the film 110 andthe glass substrate 120 into the crack mitigating layer 130. In suchembodiments, the crack may propagate through the crack mitigating layer130 in a direction substantially parallel to the film-crack mitigatinglayer interface and/or the crack mitigating layer-glass substrateinterface. In one or more embodiments, the article including the crackmitigating layer 130 may exhibit an improved average flexural strengthover articles without the crack mitigating layer 130.

The following theoretical fracture mechanics analysis illustratesselected ways in which cracks may bridge within an article. FIG. 2 is aschematic illustrating the presence of a crack in a film disposed on aglass substrate and its possible bridging modes. The numbered elementsin FIG. 2 are the glass substrate 10, the film 12 on top of a surface(unnumbered) of glass substrate 10, a two-sided deflection 14 into theinterface between glass substrate 10 and film 12, an arrest 16 which isa crack that started to develop in film 12 but did not go completelythrough film 12, a “kinking” 18 which is a crack that developed in thesurface of film 12, but when it reached the surface of the glasssubstrate 10 it did not penetrate into the glass substrate 12, insteadit moved in a lateral direction as indicated in FIG. 2 and thenpenetrates the surface of the glass substrate 10 at another position, apenetration crack 11 that developed in the film 12 and penetrated intothe glass substrate 10, a one-sided deflection 13, and a graph oftension vs. compression 17 in the glass substrate 10 compared to zeroaxis 15. Note that this schematic is not to scale and the glasssubstrate thickness typically extends further past the bottom of thefigure (not shown). As illustrated, upon application of external loading(in such cases, tensile loading is the most detrimental situation), theflaws in the film can be preferentially activated to form cracks priorto the development of cracks in the residually compressed glasssubstrate. In the scenarios illustrated in FIG. 2, with continuedincrease of external loading, the cracks will bridge until theyencounter the glass substrate. When the cracks reach the surface ofsubstrate 10 the possible bridging modes of the crack, when itoriginates in the film are: (a) penetration into the glass substratewithout changing its path as represented by numeral 11; (b) deflectioninto one side along the interface between the film and the glasssubstrate as indicated by numeral 13; (c) deflection into two sidesalong the interface as indicated by numeral 14, (d) first deflectionalong the interface and then kinking into the glass substrate asindicated by numeral 18, or (e) crack arrest as indicated by numeral 16due to microscopic deformation mechanisms, for example, plasticity,nano-scale blunting, or nano-scale deflection at the crack tip. Cracksmay originate in the film and may bridge into the glass substrate. Theabove described bridging modes are also applicable where cracksoriginate in the glass substrate and bridge into the film, for examplewhere pre-existing cracks or flaws in the glass substrate may induce ornucleate cracks or flaws in the film, thus leading to crack growth orpropagation from the glass substrate into the film, resulting in crackbridging.

Crack penetration into the glass substrate and/or film reduces theaverage flexural strength of the article and the glass substrate ascompared to the average flexural strength of the glass substrate alone(i.e., without a film or a crack mitigating layer), while crackdeflection, crack blunting or crack arrest (collectively referred toherein as crack mitigation) is preferable to help retain the averageflexural strength of the article. Crack blunting and crack arrest can bedistinguished from one another. Crack blunting may comprise anincreasing crack tip radius, for example, through plastic deformation oryielding mechanisms. Crack arrest, on the other hand, could comprise anumber of different mechanisms such as, for example, encountering ahighly compressive stress at the crack tip, a reduction of the stressintensity factor at the crack tip resulting from the presence of alow-elastic modulus interlayer or a low-elastic modulus-to-high-elasticmodulus interface transition; nano-scale crack deflection or cracktortuosity as in some polycrystalline or composite materials, strainhardening at the crack tip and the like.

Without being bound by theory, certain possible crack bridging paths canbe analyzed in the context of linear elastic fracture mechanics. In thefollowing paragraphs, one crack path is used as an example and thefracture mechanics concept is applied to the crack path to analyze theproblem and illustrate the requirements of material parameters to helpretain the average flexural strength performance of the article, for aparticular range of materials properties.

FIG. 3 below shows the illustration of the theoretical model framework.This is a simplified schematic view of the interface region between thefilm 12 and glass substrate 10. The terms μ₁, E₁, ν₁, and μ₂, E₂, ν₂,are shear modulus, Young's modulus, Poisson's ratio of glass substrateand film materials, Γ_(c) ^(Glass) and Γ_(c) ^(IT) are critical energyrelease rate of glass substrate and the interface between substrate andfilm, respectively.

The common parameters to characterize the elastic mismatch between thefilm and the substrate are Dundurs' parameters α and β [1], as definedbelow

$\begin{matrix}{\alpha = \frac{{\overset{\_}{E}}_{1} - {\overset{\_}{E}}_{2}}{{\overset{\_}{E}}_{1} + {\overset{\_}{E}}_{2}}} & (1)\end{matrix}$where Ē=E/(1−ν²) for plain strain and

$\begin{matrix}{\beta = {\frac{1}{2}\frac{{\mu_{1}\left( {1 - {2v_{2}}} \right)} - {\mu_{2}\left( {1 - {2v_{1}}} \right)}}{{\mu_{1}\left( {1 - v_{2}} \right)} + {\mu_{2}\left( {1 - v_{1}} \right)}}}} & (2)\end{matrix}$

It is worth pointing out that critical energy release rate is closelyrelated with the fracture toughness of the material through therelationship defined as

$\begin{matrix}{\Gamma = {\frac{1 - v^{2}}{E}K_{C}^{2}}} & (3)\end{matrix}$

Under the assumption that there is a pre-existing flaw in the film, upontensile loading the crack will extend vertically down as illustrated inFIG. 3. Right at the interface, the crack tends to deflect along theinterface if

$\begin{matrix}{\frac{G_{d}}{G_{p}} \geq \frac{\Gamma_{c}^{IT}}{\Gamma_{c}^{Glass}}} & (4)\end{matrix}$and the crack will penetrate into the glass substrate if

$\begin{matrix}{\frac{G_{d}}{G_{p}} \leq \frac{\Gamma_{c}^{IT}}{\Gamma_{c}^{Glass}}} & (5)\end{matrix}$where G_(d) and G_(p) and are energy release rates between deflectedcrack along the interface and the penetrated crack into the glasssubstrate [1]. On the left hand side of equations (4) and (5), the ratioG_(d)/G_(p) is a strong function of elastic mismatch parameter α andweakly dependent on β; and on the right hand side, the toughness ratioΓ_(c) ^(IT)/Γ_(c) ^(Glass) is a material parameter.

FIG. 4 graphically illustrates the trend of G_(d)/G_(p) as a function ofelastic mismatch α, reproduced from reference for doubly deflectedcracks. (Ming-Yuan, H. and J. W. Hutchinson, Crack deflection at aninterface between dissimilar elastic materials. International Journal ofSolids and Structures, 1989. 25(9): p. 1053-1067).

It is evident that the ratio G_(d)/G_(p) is strongly dependent on α.Negative α means the film is stiffer than the glass substrate andpositive α means the film is softer than the glass substrate. Thetoughness ratio Γ_(c) ^(IT)/Γ_(c) ^(Glass), which is independent of α isa horizontal line in FIG. 4. If criterion (4) is satisfied, in FIG. 4,at the region above the horizontal line, the crack tends to deflectalong the interface and therefore is beneficial for the retention of asubstrate's average flexural strength. On the other hand, if thecriterion (5) is satisfied, in FIG. 4, at the region below thehorizontal line, the crack tends to penetrate into glass substrateresulting in degradation of the average flexural strength.

With the above concept, in the following, an indium-tin-oxide (ITO) filmis utilized as an illustrative example. For glass substrate, E₁=72 GPa,ν₁=0.22, and K_(Ic)=0.7 MPa m^(1/2); for ITO, E₂=99.8 GPa, ν₂=0.25.(Zeng, K., et al., Investigation of mechanical properties of transparentconducting oxide thin films. Thin Solid Films, 2003. 443(1-2): p.60-65). The interfacial toughness between the ITO film and glasssubstrate can be approximately Γ_(in)=5 J/m², depending on depositionconditions. (Cotterell, B. and Z. Chen, Buckling and cracking of thinfilms on compliant substrates under compression. International Journalof Fracture, 2000. 104(2): p. 169-179). This will give the elasticmismatch α=−0.17 and Γ_(c) ^(IT)/Γ_(c) ^(Glass)=0.77. These values areplotted in FIG. 4. This fracture analysis predicts that the crackpenetration into the glass substrate for the ITO film leading todegradation of the average flexural strength of the glass. This isbelieved to be one of the potential underlying mechanisms observed withvarious indium-tin-oxide or other transparent conductive oxide filmsthat are disposed on glass substrates, including strengthened or strongglass substrates. As shown in FIG. 4, one way to mitigate thedegradation of the average flexural strength can be to selectappropriate materials to change the elastic mismatch α (choice 1) or toadjust the interfacial toughness (choice 2).

The theoretical analysis outlined above suggests that a crack mitigatinglayer 130 can be used to better retain the article strength.Specifically, the insertion of a crack mitigating layer between a glasssubstrate 120 and a film 110 makes crack mitigation, as defined herein,a more preferred path and thus the article is better able to retain itsstrength. In some embodiments, the stress intensity factor of a crackoriginating in the film may be modified to suppress or prevent thegrowth of the crack from the film into the glass substrate when there isa mitigating layer 130.

Glass Substrate

Referring to FIG. 1, the article 100 includes a glass substrate 120,which may be strengthened or strong, as described herein, havingopposing major surfaces 122, 124, a film 110 disposed on a at least oneopposing major surface (122 or 124) and a crack mitigating layer 130disposed between the film 110 and the glass substrate 120. In one ormore alternative embodiments, the crack mitigating layer 130 and thefilm 110 may be disposed on the minor surface(s) of the glass substratein addition to or instead of being disposed on at least one majorsurface (122 or 124). As used herein, the glass substrate 120 may besubstantially planar sheets, although other embodiments may utilize acurved or otherwise shaped or sculpted glass substrate. The glasssubstrate 120 may be substantially clear, transparent and free fromlight scattering. The glass substrate may have a refractive index in therange from about 1.45 to about 1.55. In one or more embodiments, theglass substrate 120 may be strengthened or characterized as strong, aswill be described in greater detail herein. The glass substrate 120 maybe relatively pristine and flaw-free (for example, having a low numberof surface flaws or an average surface flaw size less than about 1micron) before such strengthening. Where strengthened or strong glasssubstrates 120 are utilized, such substrates may be characterized ashaving a high average flexural strength (when compared to glasssubstrates that are not strengthened or strong) or high surfacestrain-to-failure (when compared to glass substrates that are notstrengthened or strong) on one or more major opposing surfaces of suchsubstrates.

Additionally or alternatively, the thickness of the glass substrate 120may vary along one or more of its dimensions for aesthetic and/orfunctional reasons. For example, the edges of the glass substrate 120may be thicker as compared to more central regions of the glasssubstrate 120. The length, width and thickness dimensions of the glasssubstrate 120 may also vary according to the article 100 application oruse.

The glass substrate 120 according to one or more embodiments includes anaverage flexural strength that may be measured before and after theglass substrate 120 is combined with the film 110, crack mitigatinglayer 130 and/or other films or layers. In one or more embodimentsdescribed herein, the article 100 retains its average flexural strengthafter the combination of the glass substrate 120 with the film 110,crack mitigating layer 130 and/or other films, layers or materials, whencompared to the average flexural strength of the glass substrate 120before such combination. In other words, the average flexural strengthof the article 100 is substantially the same before and after the film110, crack mitigating layer 130 and/or other films or layers aredisposed on the glass substrate 120. In one or more embodiments, thearticle 100 has an average flexural strength that is significantlygreater than the average flexural strength of a similar article thatdoes not include the crack mitigating layer 130 (e.g. higher strengththan an article that comprises film 110 and glass substrate 120 indirect contact, without an intervening crack mitigating layer).

In accordance with one or more embodiments, the glass substrate 120 hasan average strain-to-failure that may be measured before and after theglass substrate 120 is combined with the film 110, crack mitigatinglayer 130 and/or other films or layers. The term “averagestrain-to-failure” refers to the strain at which cracks propagatewithout application of additional load, typically leading tocatastrophic failure in a given material, layer or film and, perhapseven bridge to another material, layer, or film, as defined herein.Average strain-to-failure may be measured using, for example,ball-on-ring testing. Without being bound by theory, the averagestrain-to-failure may be directly correlated to the average flexuralstrength using appropriate mathematical conversions. In specificembodiments, the glass substrate 120, which may be strengthened orstrong as described herein, has an average strain-to-failure that is0.5% or greater, 0.6% or greater, 0.7% or greater, 0.8% or greater, 0.9%or greater, 1% or greater, 1.1% or greater, 1.2% or greater, 1.3% orgreater, 1.4% or greater 1.5% or greater or even 2% or greater. Inspecific embodiments, the glass substrate has an averagestrain-to-failure of 1.2%, 1.4%, 1.6%, 1.8%, 2.2%, 2.4%, 2.6%, 2.8% or3% or greater. The average strain-to-failure of the film 110 may be lessthan the average strain-to-failure of the glass substrate 120 and/or theaverage strain-to-failure of the crack mitigating layer 130. Withoutbeing bound by theory, it is believed that the average strain-to-failureof a glass substrate or any other material is dependent on the surfacequality of such material. With respect to glass substrates, the averagestrain-to-failure of a specific glass substrate is dependent on theconditions of ion exchange or strengthening process utilized in additionto or instead of the surface quality of the glass substrate.

In one or more embodiments, the glass substrate 120 retains its averagestrain-to-failure after combination with the film 110, crack mitigatinglayer 130 and/or other films or layers. In other words, the averagestrain-to-failure of the glass substrate 120 is substantially the samebefore and after the film 110, crack mitigating layer 130 and/or otherfilms or layers are disposed on the glass substrate 120. In one or moreembodiments, the article 100 has an average strain-to-failure that issignificantly greater than the average strain-to-failure of a similararticle that does not include the crack mitigating layer 130 (e.g.higher strain-to-failure than an article that comprises film 110 andglass substrate 120 in direct contact, without an intervening crackmitigating layer). For example, the article 100 may exhibit an averagestrain-to-failure that is at least 10% higher, 25% higher, 50% higher,100% higher, 200% higher or 300% higher than the averagestrain-to-failure of a similar article that does not include the crackmitigating layer 130.

The glass substrate 120 may be provided using a variety of differentprocesses. For instance, example glass substrate forming methods includefloat glass processes and down-draw processes such as fusion draw andslot draw.

In the float glass process, a glass substrate that may be characterizedby smooth surfaces and uniform thickness is made by floating moltenglass on a bed of molten metal, typically tin. In an example process,molten glass that is fed onto the surface of the molten tin bed forms afloating glass ribbon. As the glass ribbon flows along the tin bath, thetemperature is gradually decreased until the glass ribbon solidifiesinto a solid glass substrate that can be lifted from the tin ontorollers. Once off the bath, the glass substrate can be cooled furtherand annealed to reduce internal stress.

Down-draw processes produce glass substrates having a uniform thicknessthat may possess relatively pristine surfaces. Because the averageflexural strength of the glass substrate is controlled by the amount andsize of surface flaws, a pristine surface that has had minimal contacthas a higher initial strength. When this high strength glass substrateis then further strengthened (e.g., chemically), the resultant strengthcan be higher than that of a glass substrate with a surface that hasbeen lapped and polished. Down-drawn glass substrates may be drawn to athickness of less than about 2 mm. In addition, down drawn glasssubstrates may have a very flat, smooth surface that can be used in itsfinal application without costly grinding and polishing.

The fusion draw process, for example, uses a drawing tank that has achannel for accepting molten glass raw material. The channel has weirsthat are open at the top along the length of the channel on both sidesof the channel. When the channel fills with molten material, the moltenglass overflows the weirs. Due to gravity, the molten glass flows downthe outside surfaces of the drawing tank as two flowing glass films.These outside surfaces of the drawing tank extend down and inwardly sothat they join at an edge below the drawing tank. The two flowing glassfilms join at this edge to fuse and form a single flowing glasssubstrate. The fusion draw method offers the advantage that, because thetwo glass films flowing over the channel fuse together, neither of theoutside surfaces of the resulting glass substrate comes in contact withany part of the apparatus. Thus, the surface properties of the fusiondrawn glass substrate are not affected by such contact.

The slot draw process is distinct from the fusion draw method. In slotdraw processes, the molten raw material glass is provided to a drawingtank. The bottom of the drawing tank has an open slot with a nozzle thatextends the length of the slot. The molten glass flows through theslot/nozzle and is drawn downward as a continuous substrate and into anannealing region.

Once formed, glass substrates may be strengthened to form strengthenedglass substrates. As used herein, the term “strengthened glasssubstrate” may refer to a glass substrate that has been chemicallystrengthened, for example through ion-exchange of larger ions forsmaller ions in the surface of the glass substrate. However, otherstrengthening methods known in the art, such as thermal tempering, maybe utilized to form strengthened glass substrates. As will be described,strengthened glass substrates may include a glass substrate having asurface compressive stress in its surface that aids in the strengthpreservation of the glass substrate. Strong glass substrates are alsowithin the scope of this disclosure and include glass substrates thatmay not have undergone a specific strengthening process, and may nothave a surface compressive stress, but are nevertheless strong. Suchstrong glass substrates articles may be defined as glass sheet articlesor glass substrates having an average strain-to-failure greater thanabout 0.5%, 0.7%, 1%, 1.5%, or even greater than 2%. Such strong glasssubstrates can be made, for example, by protecting the pristine glasssurfaces after melting and forming the glass substrate. An example ofsuch protection occurs in a fusion draw method, where the surfaces ofthe glass films do not come into contact with any part of the apparatusor other surface after forming. The glass substrates formed from afusion draw method derive their strength from their pristine surfacequality. A pristine surface quality can also be achieved through etchingor polishing and subsequent protection of glass substrate surfaces, andother methods known in the art. In one or more embodiments, bothstrengthened glass substrates and the strong glass substrates maycomprise glass sheet articles having an average strain-to-failuregreater than about 0.5%, 0.7%, 1%, 1.5%, or even greater than 2%, forexample when measured using ring-on-ring or ball-on-ring flexuraltesting.

As mentioned above, the glass substrates described herein may bechemically strengthened by an ion exchange process to provide astrengthened glass substrate 120. The glass substrate may also bestrengthened by other methods known in the art, such as thermaltempering. In the ion-exchange process, typically by immersion of theglass substrate into a molten salt bath for a predetermined period oftime, ions at or near the surface(s) of the glass substrate areexchanged for larger metal ions from the salt bath. In one embodiment,the temperature of the molten salt bath is about 350° C. to 450° C. andthe predetermined time period is about two to about eight hours. Theincorporation of the larger ions into the glass substrate strengthensthe glass substrate by creating a compressive stress in a near surfaceregion or in regions at and adjacent to the surface(s) of the glasssubstrate. A corresponding tensile stress is induced within a centralregion or regions at a distance from the surface(s) of the glasssubstrate to balance the compressive stress. Glass substrates utilizingthis strengthening process may be described more specifically aschemically-strengthened glass substrates 120 or ion-exchanged glasssubstrates 120. Glass substrates that are not strengthened may bereferred to herein as non-strengthened glass substrates.

In one example, sodium ions in a strengthened glass substrate 120 arereplaced by potassium ions from the molten bath, such as a potassiumnitrate salt bath, though other alkali metal ions having larger atomicradii, such as rubidium or cesium, can replace smaller alkali metal ionsin the glass. According to particular embodiments, smaller alkali metalions in the glass can be replaced by Ag⁺ ions. Similarly, other alkalimetal salts such as, but not limited to, sulfates, phosphates, halides,and the like may be used in the ion exchange process.

The replacement of smaller ions by larger ions at a temperature belowthat at which the glass network can relax produces a distribution ofions across the surface(s) of the strengthened glass substrate 120 thatresults in a stress profile. The larger volume of the incoming ionproduces a compressive stress (CS) on the surface and tension (centraltension, or CT) in the center of the strengthened glass substrate 120.The compressive stress is related to the central tension by thefollowing relationship:

${CS} = {C{T\left( \frac{t - {2DOL}}{DOL} \right)}}$where t is the total thickness of the strengthened glass substrate 120and compressive depth of layer (DOL) is the depth of exchange. Depth ofexchange may be described as the depth within the strengthened glasssubstrate 120 (i.e., the distance from a surface of the glass substrateto a central region of the glass substrate), at which ion exchangefacilitated by the ion exchange process takes place.

In one embodiment, a strengthened glass substrate 120 can have a surfacecompressive stress of 300 MPa or greater, e.g., 400 MPa or greater, 450MPa or greater, 500 MPa or greater, 550 MPa or greater, 600 MPa orgreater, 650 MPa or greater, 700 MPa or greater, 750 MPa or greater or800 MPa or greater. The strengthened glass substrate 120 may have acompressive depth of layer 15 μm or greater, 20 μm or greater (e.g., 25μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or greater) and/or a centraltension of 10 MPa or greater, 20 MPa or greater, 30 MPa or greater, 40MPa or greater (e.g., 42 MPa, 45 MPa, or 50 MPa or greater) but lessthan 100 MPa (e.g., 95, 90, 85, 80, 75, 70, 65, 60, 55 MPa or less). Inone or more specific embodiments, the strengthened glass substrate 120has one or more of the following: a surface compressive stress greaterthan 500 MPa, a depth of compressive layer greater than 15 μm, and acentral tension greater than 18 MPa.

Without being bound by theory, it is believed that strengthened glasssubstrates 120 with a surface compressive stress greater than 500 MPaand a compressive depth of layer greater than about 15 μm typically havegreater strain-to-failure than non-strengthened glass substrates (or, inother words, glass substrates that have not been ion exchanged orotherwise strengthened). In some embodiments, the benefits of one ormore embodiments described herein may not be as prominent withnon-strengthened or weakly strengthened types of glass substrates thatdo not meet these levels of surface compressive stress or compressivedepth of layer, because of the presence of handling or common glasssurface damage events in many typical applications. However, asmentioned previously, in other specific applications where the glasssubstrate surfaces can be adequately protected from scratches or surfacedamage (for example by a protective coating or other layers), strongglass substrates with a relatively high strain-to-failure can also becreated through forming and protection of a pristine glass surfacequality, using methods such as the fusion forming method. In thesealternate applications, the benefits of one or more embodimentsdescribed herein can be similarly realized.

Example ion-exchangeable glasses that may be used in the strengthenedglass substrate 120 may include alkali aluminosilicate glasscompositions or alkali aluminoborosilicate glass compositions, thoughother glass compositions are contemplated. As used herein, “ionexchangeable” means that a glass substrate is capable of exchangingcations located at or near the surface of the glass substrate withcations of the same valence that are either larger or smaller in size.One example glass composition comprises SiO₂, B₂O₃ and Na₂O, where(SiO₂+B₂O₃)≥66 mol. %, and Na₂O≥9 mol. %. In an embodiment, the glasssubstrate 120 includes a glass composition with at least 6 wt. %aluminum oxide. In a further embodiment, a glass substrate 120 includesa glass composition with one or more alkaline earth oxides, such that acontent of alkaline earth oxides is at least 5 wt. %. Suitable glasscompositions, in some embodiments, further comprise at least one of K₂O,MgO, and CaO. In a particular embodiment, the glass compositions used inthe glass substrate 120 can comprise 61-75 mol. % SiO₂; 7-15 mol. %Al₂O₃; 0-12 mol. % B₂O₃; 9-21 mol. % Na₂O; 0-4 mol. % K₂O; 0-7 mol. %MgO; and 0-3 mol. % CaO.

A further example glass composition suitable for the glass substrate120, which may optionally be strengthened or strong, comprises: 60-70mol. % SiO₂; 6-14 mol. % Al₂O₃; 0-15 mol. % B₂O₃; 0-15 mol. % Li₂O; 0-20mol. % Na₂O; 0-10 mol. % K₂O; 0-8 mol. % MgO; 0-10 mol. % CaO; 0-5 mol.% ZrO₂; 0-1 mol. % SnO₂; 0-1 mol. % CeO₂; less than 50 ppm As₂O₃; andless than 50 ppm Sb₂O₃; where 12 mol. %≤(Li₂O+Na₂O+K₂O)≤20 mol. % and 0mol. %≤(MgO+CaO)≤10 mol. %.

A still further example glass composition suitable for the glasssubstrate 120, which may optionally be strengthened or strong,comprises: 63.5-66.5 mol. % SiO₂; 8-12 mol. % Al₂O₃; 0-3 mol. % B₂O₃;0-5 mol. % Li₂O; 8-18 mol. % Na₂O; 0-5 mol. % K₂O; 1-7 mol. % MgO; 0-2.5mol. % CaO; 0-3 mol. % ZrO₂; 0.05-0.25 mol. % SnO₂; 0.05-0.5 mol. %CeO₂; less than 50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 14 mol.%≤(Li₂O+Na₂O+K₂O)≤18 mol. % and 2 mol. %≤(MgO+CaO)≤7 mol. %.

In a particular embodiment, an alkali aluminosilicate glass compositionsuitable for the glass substrate 120, which may optionally bestrengthened or strong, comprises alumina, at least one alkali metaland, in some embodiments, greater than 50 mol. % SiO₂, in otherembodiments at least 58 mol. % SiO₂, and in still other embodiments atleast 60 mol. % SiO₂, wherein the ratio

${\frac{{{Al}_{2}O_{3}} + {B_{2}O_{3}}}{\sum{modifiers}} > 1},$where in the ratio the components are expressed in mol. % and themodifiers are alkali metal oxides. This glass composition, in particularembodiments, comprises: 58-72 mol. % SiO₂; 9-17 mol. % Al₂O₃; 2-12 mol.% B₂O₃; 8-16 mol. % Na₂O; and 0-4 mol. % K₂O, wherein the ratio

$\frac{{{Al}_{2}O_{3}} + {B_{2}O_{3}}}{\sum{modifiers}} > 1.$

In still another embodiment, the glass substrate, which may optionallybe strengthened or strong, may include an alkali aluminosilicate glasscomposition comprising: 64-68 mol. % SiO₂; 12-16 mol. % Na₂O; 8-12 mol.% Al₂O₃; 0-3 mol. % B₂O₃; 2-5 mol. % K₂O; 4-6 mol. % MgO; and 0-5 mol. %CaO, wherein: 66 mol. %≤SiO₂+B₂O₃+CaO≤69 mol. %;Na₂O+K₂O+B₂O₃+MgO+CaO+SrO>10 mol. %; 5 mol. %≤MgO+CaO+SrO≤8 mol. %;(Na₂O+B₂O₃)—Al₂O₃≤2 mol. %; 2 mol. %≤Na₂O—Al₂O₃≤6 mol. %; and 4 mol.%≤(Na₂O+K₂O)—Al₂O₃≤10 mol. %.

In some embodiments, the glass substrate 120, which may optionally bestrengthened or strong, may comprise an alkali silicate glasscomposition comprising: 2 mol % or more of Al₂O₃ and/or ZrO₂, or 4 mol %or more of Al₂O₃ and/or ZrO₂.

In some embodiments, the glass substrate used in the glass substrate 120may be batched with 0-2 mol. % of at least one fining agent selectedfrom a group that includes Na₂SO₄, NaCl, NaF, NaBr, K₂SO₄, KCl, KF, KBr,and SnO₂.

The glass substrate 120 according to one or more embodiments can have athickness ranging from about 50 μm to 5 mm. Example glass substrate 120thicknesses range from 100 μm to 500 μm, e.g., 100, 200, 300, 400 or 500μm. Further example glass substrate 120 thicknesses range from 500 μm to1000 μm, e.g., 500, 600, 700, 800, 900 or 1000 μm. The glass substrate120 may have a thickness greater than 1 mm, e.g., about 2, 3, 4, or 5mm. In one or more specific embodiments, the glass substrate 120 mayhave a thickness of 2 mm or less or less than 1 mm. The glass substrate120 may be acid polished or otherwise treated to remove or reduce theeffect of surface flaws.

Film

The article 100 includes a film 110 disposed on a surface of the glasssubstrate 120. The film 110 may be disposed on one or both majorsurfaces 122, 124 of the glass substrate 120. In one or moreembodiments, the film 110 may be disposed on one or more minor surfaces(not shown) of the glass substrate 120 in addition to or instead ofbeing disposed on one or both major surfaces 122, 124. In one or moreembodiments, the film 110 is free of macroscopic scratches or defectsthat are easily visible to the eye.

In one or more embodiments, the film may lower the average flexuralstrength of articles incorporating such films and glass substrate,through the mechanisms described herein In one or more embodiments, suchmechanisms include instances in which the film may lower the averageflexural strength of the article because crack(s) developing in suchfilm bridge into the glass substrate. In other embodiments, themechanisms include instances in which the film may lower the averageflexural strength of the article because cracks developing in the glasssubstrates bridge into the film. The film of one or more embodiments mayexhibit a strain-to-failure of 2% or less or a strain-to-failure that isless than the strain to failure of the glass substrates describedherein. films including any of these attributes may be characterized asbrittle.

In accordance with one or more embodiments, the film 110 may have astrain-to-failure (or crack onset strain level) that is lower than thestrain-to-failure of the glass substrate 120. For example, the film 110may have strain-to-failure of about 2% or less, about 1.8% or less,about 1.6% or less, about 1.5% or less, about 1.4% or less, about 1.2%or less, about 1% or less, about 0.8% or less, about 0.6% or less, about0.5% or less, about 0.4% or less or about 0.2% or less. In someembodiments, the strain-to-failure of the film 110 may be lower thanthat the strain-to-failure of the strengthened glass substrates 120 thathave a surface compressive stress greater than 500 MPa and a compressivedepth of layer greater than about 15 μm. In one or more embodiments, thefilm 110 may have a strain-to-failure that is at least 0.1% lower orless, or in some cases, at least 0.5% lower or less than thestrain-to-failure of the glass substrate 120. In one or moreembodiments, the film 110 may have a strain-to-failure that is at least0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.55%, 0.6%, 0.65%, 0.7%,0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1% lower or less than thestrain-to-failure of the glass substrate 120.

Exemplary films 110 may have an elastic modulus of at least 25 GPaand/or a hardness of at least 1.75 GPa, although some combinationsoutside of this range are possible. In some embodiments the film 110 mayhave an elastic modulus 50 GPa or greater or even 70 GPa or greater. Forexample, the film elastic modulus may be 55 GPa, 60 GPa, 65 GPa, 75 GPa,80 GPa, 85 GPa or more. In one or more embodiments, the film 110 mayhave a hardness greater than 3.0 GPa. For example, the film 110 may havea hardness of 5 GPa, 5.5 GPa, 6 GPa, 6.5 GPa, 7 GPa, 7.5 GPa, 8 GPa, 8.5GPa, 9 GPa, 9.5 GPa, 10 GPa or greater. These elastic modulus andhardness values can be measured for such films 110 using known diamondnano-indentation methods that are commonly used for determining theelastic modulus and hardness of films. Exemplary diamondnano-indentation methods may utilize a Berkovich diamond indenter.

The films 110 described herein may also exhibit a fracture toughnessless than about 10 MPa·m^(1/2), or in some cases less than 5MPa·m^(1/2), or in some cases less than 1 MPa·m^(1/2). For example, thefilm may have a fracture toughness of 4.5 MPa·m^(1/2), 4 MPa·m^(1/2),3.5 MPa·m^(1/2), 3 MPa·m^(1/2), 2.5 MPa·m^(1/2), 2 MPa·m^(1/2), 1.5MPa·m^(1/2), 1.4 MPa·m^(1/2), 1.3 MPa·m^(1/2), 1.2 MPa·m^(1/2), 1.1MPa·m^(1/2), 0.9 MPa·m^(1/2), 0.8 MPa·m^(1/2), 0.7 MPa·m^(1/2), 0.6MPa·m^(1/2), 0.5 MPa·m^(1/2), 0.4 MPa·m^(1/2), 0.3 MPa·m^(1/2), 0.2MPa·m^(1/2), 0.1 MPa·m^(1/2) or less.

The films 110 described herein may also have a critical strain energyrelease rate (G_(IC)=K_(IC) ²/E) that is less than about 0.1 kJ/m², orin some cases less than 0.01 kJ/m². In one or more embodiments, the film110 may have a critical strain energy release rate of 0.09 kJ/m², 0.08kJ/m², 0.07 kJ/m², 0.06 kJ/m², 0.05 kJ/m², 0.04 kJ/m², 0.03 kJ/m², 0.02kJ/m², 0.0075 kJ/m², 0.005 kJ/m², 0.0025 kJ/m² or less.

In one or more embodiments, the film 110 may include a plurality oflayers. In one or more embodiments, each of the layers of the film maybe characterized as brittle based on one or more of the layer's impacton the average flexural strength of the article and/or the layer'sstrain-to-failure, fracture toughness, or critical strain energy releaserate values, as otherwise described herein. In one variant, the layersof the film 110 need not have identical properties such as elasticmodulus and/or fracture toughness. In another variant, the layers of thefilm 110 may include different materials from one another.

In one or more embodiments, the film 110 may have a tensile stress thatwas built in the film or introduced into the film during deposition orformation. In some cases, the tensile stress into the film 110 may bedifficult to avoid while retaining the other desired properties. Thistensile stress can cause a film 110 to crack or fail more readily, forexample, in some cases this tensile stress may lower thestrain-to-failure (crack onset strain) of the film 110. Moreover, cracksoriginating in the film 110 can bridge more readily from the film 110into the glass substrate 120 under the right conditions, due in part tothe tensile stress. Additionally or alternatively, the tensile stress inthe film 110 may cause the a film 110 to crack or fail more readilybecause cracks originating in the glass substrate 120 can bridge morereadily from the glass substrate 120 into the film 110 under the rightconditions. As will be described in greater detail below, the crackmitigating layer 130 may allow the film 110 to relax during depositionor formation, where the film is disposed on the glass substrate 120after the crack mitigating layer 130 is disposed on the glass substrate120. Additionally or alternatively, the crack mitigating layer 130 mayreduce the amount of stress that is created locally in the film 110during loading (i.e., during the application of an external force on thefilm, such as the flexure experienced by the film during ring-on-ringtesting), or during flexure of the article 100.

The compositions or material(s) of the film 110 are not particularlylimited. Some non-limiting examples of film 110 materials include oxidessuch as SiO₂, Al₂O₃, TiO₂, Nb₂O₅, Ta₂O₅; oxynitrides such asSiO_(x)N_(y), SiAl_(x)O_(y)N_(z), and AlO_(x)N_(y); nitrides such asSiN_(x), AlN_(x), cubic boron nitride, and TiN_(x); carbides such asSiC, TiC, and WC; combinations of the above such as oxycarbides andoxy-carbo-nitrides (for example, SiC_(x)O_(y) and SiC_(x)O_(y)N_(z));semiconductor materials such as Si and Ge; transparent conductors suchas indium-tin-oxide, tin oxide, fluorinated tin oxide, aluminum zincoxide, or zinc oxide; carbon nanotube or graphene-doped oxides; silveror other metal-doped oxides, highly siliceous polymers such as highlycured siloxanes and silsesquioxanes; diamond or diamond-like-carbonmaterials; or selected metal films which can exhibit a fracturebehavior.

The film 110 can be disposed on the glass substrate 120 by vacuumdeposition techniques, for example, chemical vapor deposition (e.g.,plasma enhanced chemical vapor deposition or atmospheric pressurechemical vapor deposition), physical vapor deposition (e.g., reactive ornonreactive sputtering or laser ablation), thermal, resistive, or e-beamevaporation, or atomic layer deposition. The film 110 may also bedisposed on one or more surfaces 122, 124 of the glass substrate 120using liquid-based techniques, for example sol-gel coating or polymercoating methods, for example spin, spray, slot draw, slide, wire-woundrod, blade/knife, air knife, curtain, gravure, and roller coating amongothers. In some embodiments it may be desirable to use adhesionpromoters, such as silane-based materials, between the film 110 and theglass substrate 120, between the glass substrate 120 and crackmitigating layer 130, between the layers (if any) of the crackmitigating layer 130, between the layers (if any) of the film 110 and/orbetween the film 110 and the crack mitigating layer 130. In one or morealternative embodiments, the film 110 may be disposed on the glasssubstrate 120 as a transfer layer.

The film 110 thickness can vary depending on the intended use of thearticle 100. In one embodiment the film 110 thickness may be in theranges from about 0.01 μm to about 0.5 μm or from about 0.01 μm to about20 μm. In another embodiment, the film 110 may have a thickness in therange from about 0.05 μm to about 10 μm, from about 0.05 μm to about 0.5μm, from about 0.01 μm to about 0.15 μm or from about 0.015 μm to about0.2 μm.

In some embodiments it may be advantageous to include a material in thefilm 110 that has either:

(1) a refractive index that is similar to the refractive index of eitherthe glass substrate 120, the crack mitigating layer 130 and/or otherfilms or layers in order to minimize optical interference effects;

(2) a refractive index (real and/or imaginary components) that is tunedto achieve anti-reflective interference effects; and/or

(3) a refractive index (real and/or imaginary components) that is tunedto achieve wavelength-selective reflective or wavelength-selectiveabsorptive effects, such as to achieve UV or IR blocking or reflection,or to achieve coloring/tinting effects.

In one or more embodiments, the film 110 may have a refractive indexthat is greater than the refractive index of the glass substrate 120and/or greater than the refractive index of the crack mitigating layer130. In one or more embodiments, the film may have a refractive index inthe range from about 1.7 to about 2.2, or in the range from about 1.4 toabout 1.6, or in the range from about 1.6 to about 1.9.

The film 110 may also serve multiple functions, or be integrated withfilms or layers that serve other functions than the film 110 or even thesame function(s) as the film 110. The film 110 may include UV or IRlight reflecting or absorbing layers, anti-reflection layers, anti-glarelayers, dirt-resistant layers, self-cleaning layers, scratch-resistantlayers, barrier layers, passivation layers, hermetic layers,diffusion-blocking layers, fingerprint-resistant layers, and the like.Further, the film 110 may include conducting or semi-conducting layers,thin film transistor layers, EMI shielding layers, breakage sensors,alarm sensors, electrochromic materials, photochromic materials, touchsensing layers, or information display layers. The film 110 and/or anyof the foregoing layers may include colorants or tint. When informationdisplay layers are integrated into the article 100, the article 100 mayform part of a touch-sensitive display, a transparent display, or aheads-up display. It may be desirable that the film 110 performs aninterference function, which selectively transmits, reflects, or absorbsdifferent wavelengths or colors of light. For example, the films 110 mayselectively reflect a targeted wavelength in a heads-up displayapplication.

Functional properties of the film 110 may include optical properties,electrical properties and/or mechanical properties, such as hardness,elastic modulus, strain-to-failure, abrasion resistance, mechanicaldurability, coefficient of friction, electrical conductivity, electricalresistivity, electron mobility, electron or hole carrier doping, opticalrefractive index, density, opacity, transparency, reflectivity,absorptivity, transmissivity and the like. These functional propertiesare substantially maintained or even improved after the film 110 iscombined with the glass substrate 120, crack mitigating layer 130 and/orother films included in the article 100.

Crack Mitigating Layer

The crack mitigating layer 130 according to one or more embodiments mayhave a critical strain energy release rate (G_(IC)=K_(IC) ²/E) that isgreater than the critical strain energy release rate of the film 110. Inone or more embodiments, the film 110 may have a critical strain energyrelease rate of about 0.1 kJ/m² or less and the crack mitigating layer130 may have a critical strain energy release rate of greater than about0.1 kJ/m². The crack mitigating layer 130 may have a critical strainenergy release rate of about 1.0 kJ/m² or greater. In specificembodiments, the crack mitigating layer 130 may have a critical strainenergy release rate in a range of about 0.05 kJ/m² to about 100 kJ/m²,while the film 110 may have a critical strain energy release rate lessthan about 0.05 kJ/m². The crack mitigating layer 130 may have acritical strain energy release rate in the range from about 0.05 kJ/m²to about 90 kJ/m², from about 0.5 kJ/m² to about 80 kJ/m², from about0.5 kJ/m² to about 70 kJ/m², from about 0.5 kJ/m² to about 60 kJ/m²,from about 0.5 kJ/m² to about 50 kJ/m², from about 0.5 kJ/m² to about 40kJ/m², from about 0.5 kJ/m² to about 30 kJ/m², from about 0.5 kJ/m² toabout 20 kJ/m², from about 0.5 kJ/m² to about 10 kJ/m², from about 0.5kJ/m² to about 5 kJ/m², from about 1 kJ/m² to about 100 kJ/m², fromabout 5 kJ/m² to about 100 kJ/m², from about 10 kJ/m² to about 100kJ/m², from about 20 kJ/m² to about 100 kJ/m², from about 30 kJ/m² toabout 100 kJ/m², from about 40 kJ/m² to about 100 kJ/m², from about 50kJ/m² to about 100 kJ/m², from about 60 kJ/m² to about 100 kJ/m², fromabout 70 kJ/m² to about 100 kJ/m², from about 80 kJ/m² to about 100kJ/m², from about 90 kJ/m² to about 100 kJ/m², from about 0.05 kJ/m² toabout 1 kJ/m², from about 1 kJ/m² to about 5 kJ/m², from about 5 kJ/m²to about 10 kJ/m², from about 10 kJ/m² to about 20 kJ/m², from about 20kJ/m² to about 30 kJ/m², from about 30 kJ/m² to about 40 kJ/m², fromabout 40 kJ/m² to about 50 kJ/m², from about 50 kJ/m² to about 60 kJ/m²,from about 60 kJ/m² to about 70 kJ/m², from about 70 kJ/m² to about 80kJ/m² and from about 80 kJ/m² to about 90 kJ/m².

In such embodiments, the crack mitigating layer 130 has a greatercritical strain energy release rate than the film 110 and, therefore,can release strain energy from a crack bridging from one of the film 110and the glass substrate 120 into the other of the film 110 and the glasssubstrate 120. Such strain energy release stops the crack from bridgingacross the interface between the film 110 and the glass substrate 120,or alternately may suppress the growth of cracks that are alreadybridging across the interface between the film 110 and the glasssubstrate 120, which may also be bridging through the crack mitigatinglayer 130. This suppression of crack growth may, for example, lead to ahigher required stress, strain, or load level in order to inducesignificant crack growth, relative to a similar article without thecrack mitigating layer. In some embodiments, this suppression of crackgrowth may originate from a lowered stress-intensity-factor at the tipsof bridging cracks, which may be induced by a relatively low elasticmodulus or low yield stress or significant plastic deformation of thecrack mitigating layer. In one or more embodiments, one or more of thesecrack mitigation mechanisms occurs regardless of where the crackoriginates (i.e., the film 110 or the glass substrate 120).

In accordance with one or more embodiments, the crack mitigating layer130 may have an average strain-to-failure that is greater than theaverage strain-to-failure of the film 110. In one or more embodiments,the crack mitigating layer 130 may have an average strain-to-failurethat is equal to or greater than about 0.5%, 0.7%, 1%, 1.5%, 2%, or even4%. The crack mitigating layer 130 may have an average strain-to-failureof 0.6%, 0.8%, 0.9%, 1.1%, 1.2%, 1.3%, 1.4%, 1.6%, 1.7%, 1.8%, 1.9%,2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 5% or 6% or greater.In one or more embodiments, the film 110 may have an averagestrain-to-failure (crack onset strain) that is 1.5%, 1.0%, 0.7%, 0.5%,or even 0.4% or less. The film 110 may have an average strain-to-failureof 1.4%, 1.3%, 1.2%, 1.1%, 0.9%, 0.8%, 0.6%, 0.3%, 0.2%, 0.1% or less.The average strain-to-failure of the glass substrate 120 may be greaterthan the average strain-to-failure of the film 110, and in someinstances, may be greater than the average strain-to-failure of thecrack mitigating layer 130. In some specific embodiments, the crackmitigating layer 130 may have a higher average strain-to-failure thanthe glass substrate, to minimize any negative mechanical effect of thecrack mitigating layer on the glass substrate.

In one or more embodiments, the crack mitigating layer 130 may have afracture toughness of 1 MPa·m^(1/2) or greater, for example 2MPa·m^(1/2) or greater, or 5 MPa·m^(1/2) or greater. The crackmitigating layer 130 may also have a fracture toughness in the rangefrom about 1 MPa·m^(1/2) to about 5 MPa·m^(1/2), or from about 2MPa·m^(1/2) to about 4 MPa·m^(1/2). In one or more specific embodiments,the crack mitigating layer 130 may have a fracture toughness of 6MPa·m^(1/2), 7 MPa·m^(1/2), 8 MPa·m^(1/2), 9 MPa·m^(1/2), 10 MPa·m^(1/2)or greater. In such embodiments, the crack mitigating layer 130 averagestrain-to-failure and/or fracture toughness properties prevents thecrack from bridging across the interface between the film 110 and theglass substrate 120. In one or more embodiments, this crack mitigationmechanism occurs regardless of where the crack originates (i.e., thefilm 110 or the glass substrate 120). The fracture toughness of thecrack mitigating layer 130 may alternatively be low to provide a lowtoughness crack mitigating layer, as will be described in greater detailbelow. In such embodiments, the crack mitigating layer 130 may exhibit afracture toughness that is about 50% or less than 50% of the fracturetoughness of either the glass substrate 120 or the film. In morespecific embodiments, the fracture toughness of the crack mitigatinglayer 130 may be about 25% or less than 25% of the fracture toughness ofeither the glass substrate 120 or the film. For example, the crackmitigating layer 130 may exhibit a fracture toughness of about 1MPa·m^(1/2) or less, 0.75 MPa·m^(1/2) or less, 0.5 MPa·m^(1/2) or less,0.4 MPa·m^(1/2) or less, 0.3 MPa·m^(1/2) or less, 0.25 MPa·m^(1/2) orless, 0.2 MPa·m^(1/2) or less, and all ranges and sub-ranges therebetween.

The crack mitigating layer 130 may have a refractive index that isgreater than the refractive index of the glass substrate 120. In one ormore embodiments, the refractive index of the crack mitigating layer 130may be less than the refractive index of the film 110. In a morespecific embodiment, the refractive index of the crack mitigating layer130 may be between the refractive index of the glass substrate 120 andthe film 110. For example, the refractive index of the crack mitigatinglayer 130 may be in the range from about 1.45 to about 1.95, from about1.5 to about 1.8, or from about 1.6 to about 1.75. Alternatively, thecrack mitigating layer may have a refractive index that is substantiallythe same as the glass substrate, or a refractive index that is not morethan 0.05 index units greater than or less than the glass substrate overa substantial portion of the visible wavelength range (e.g. from 450 to650 nm).

In one or more embodiments, the crack mitigating layer 130 is able towithstand high temperature processes. Such processes can include vacuumdeposition processes such as chemical vapor deposition (e.g., plasmaenhanced chemical vapor deposition), physical vapor deposition (e.g.,reactive or nonreactive sputtering or laser ablation), thermal or e-beamevaporation and/or atomic layer deposition. In one or more specificembodiments, the crack mitigating layer is able to withstand a vacuumdeposition process in which the film 110 and/or other films disposed onthe glass substrate 120 are deposited on the crack mitigating layer 130via vacuum deposition. As used herein, the term “withstand” includes theresistance of the crack mitigating layer 130 to temperatures exceeding100° C., 200° C., 300° C., 400° C. and potentially even greatertemperatures. In some embodiments, the crack mitigating layer 130 may beconsidered to withstand the vacuum deposition or temperature treatmentprocess if the crack mitigating layer 130 experiences a weight loss of10% or less, 8% or less, 6% or less, 4% or less, 2% or less or 1% orless, after deposition of the film 110 and/or other films on the glasssubstrate (and on the crack mitigating layer 130). The depositionprocess (or testing after the deposition process) under which the crackmitigating layer experiences weight loss can include temperatures ofabout 100° C. or greater, 200° C. or greater, 300° C. or greater, 400°C. or greater; environments that are rich in a specific gas (e.g.,oxygen, nitrogen, argon etc.); and/or environments in which depositionmay be performed under high vacuum (e.g. 10⁻⁶ Torr), under atmosphericconditions and/or at pressures therebetween (e.g., 10 mTorr). As will bediscussed herein, the material utilized to form the crack mitigatinglayer 130 may be specifically selected for its high temperaturetolerances (i.e., the ability to withstand high temperature processessuch as vacuum deposition processes) and/or its environmental tolerances(i.e., the ability to withstand environments rich in a specific gas orat a specific pressure). These tolerances may include high temperaturetolerance, high vacuum tolerance, low vacuum outgassing, a hightolerance to plasma or ionized gases, a high tolerance to ozone, a hightolerance to UV, a high tolerance to solvents, or a high tolerance toacids or bases. In some instances, the crack mitigating layer 130 may beselected to pass an outgassing test according to ASTM E595.

In one or more embodiments, the crack mitigating layer 130 preventsdegradation of the average flexural strength of the glass substrate 120.In another embodiment, the crack mitigating layer 130 prevents the film110 from degrading the average flexural strength of the glass substrate120. The crack mitigating layer 130 may prevent cracks from bridgingbetween the film 110 and the glass substrate 120. The crack mitigatinglayer 130 of one or more embodiments may increase the averagestrain-to-failure of the film 110 and thus, prevents degradation of theaverage flexural strength of the glass substrate 120. In one or morealternative embodiments, the crack mitigating layer 130 increases theaverage flexural strength of the article 100, when compared to articlesthat do not include such a crack mitigating layer but include a glasssubstrate and a film, as described herein.

The crack mitigating layer 130 may prevent degradation of the averagestrain-to-failure of the glass substrate 120 in some instances, while inother instances, the crack mitigating layer 130 may prevent the film 110from degrading the average strain-to-failure of the glass substrate 120.In another embodiment, the crack mitigating layer 130 prevents cracksfrom bridging between the film 110 and the glass substrate 120, thuspreventing the film 110 from degrading the average strain-to-failure ofthe glass substrate 120. In one or more alternative embodiments, thecrack mitigating layer 130 increases the average strain-to-failure ofthe article 100, when this average strain-to-failure is compared to theaverage strain-to-failure of articles that do not include a crackmitigating layer but include a glass substrate and a film, as describedherein.

In one or more embodiments, the crack mitigating layer 130 may have alow-elastic modulus and/or low-hardness. Low-elastic modulus materialsand low hardness materials substantially overlap as many low-elasticmodulus materials are also low hardness materials. However, these twoproperties (i.e., low-elastic modulus and low hardness) aredistinguished herein because they highlight two different mechanisms ormethods by which a crack can be mitigated (i.e., deflected, arrested orblunted) before bridging between the film 110 and the glass substrate120. In one or more embodiments, low-elastic modulus crack mitigatinglayers may suppress the growth of cracks that are already bridgingacross the interface between the film 110 and the glass substrate 120,which may also be bridging through the crack mitigating layer 130. Thissuppression of crack growth may, for example, lead to a higher requiredstress, strain, or load level in order to induce significant crackgrowth, relative to a similar article without the crack mitigatinglayer. The crack mitigating layer 130 may have an elastic modulus so lowthat the crack mitigating layer 130 is unable to drive or propagate acrack from one of the film 110 and glass substrate 120 to the other ofthe film 110 and glass substrate 120. In some embodiments, thissuppression of crack growth may originate from a lowered stressintensity factor at the tips of bridging cracks, which may be induced bya relatively low-elastic modulus of the crack mitigating layer. Suchcrack mitigating layers may have an elastic modulus that is less thanthe glass substrate, less than about 50 GPa, less than about 30 GPa,less than about 15 GPa or even less than about 5 GPa. The stressintensity factor is accepted as indicating the driving force for crackgrowth. A reduction in the stress intensity factor is believed to delayor suppress crack growth from the film into the glass substrate (meaninghigher load levels are required for crack growth within the glasssubstrate than would be needed without the low-elastic modulus layer).

The crack mitigating layer 130 may have a hardness that is less thanabout 3.0 GPa, less than 2.0 GPa or even less than 1.0 GPa. Theseelastic modulus and hardness values can be measured using known diamondnano-indentation methods that are commonly used for determining theelastic modulus and hardness of films. Exemplary diamondnano-indentation methods utilize a Berkovich diamond indenter.

In one or more embodiments, the crack mitigating layer 130 may alsoexhibit a low yield stress, a low shear modulus, plastic or ductiledeformation, or other known properties for strain energy release withoutfracture. In embodiments where the crack mitigating layer exhibits a lowyield stress, the yield stress may be less than 500 MPa, less than 100MPa, or even less than 10 MPa.

In embodiments in which the crack mitigating layer 130 exhibits alow-elastic modulus, low yield stress, or plastic and/or ductiledeformation behavior, the crack mitigating layer 130 can deform torelease strain energy and prevent crack bridging or propagation betweenthe film 110 and glass substrate 120. These ductile crack mitigatinglayers may also comprise the high strain-to-failure values listed abovefor the crack mitigating layer.

An exemplary crack mitigating layer 130 may be a polymeric film. Suchfilms may have a low-elastic modulus or a low Tg that cannot supporthigh values of stress within the deposited film 110, thus allowing thefilm 110 to partially relax and lower the tensile stress within, whileminimizing the transmission of stress into the glass substrate 120. Thisreduces the stress intensity factor of the flaws on the glass substrateas compared to a scenario without polymeric film.

In one or more embodiments, the crack mitigating layer 130 physicallyprevents alignment of cracks originating in the film 110 and the glasssubstrate 120. In other words, a crack present in the film 110 cannotalign with a crack present in the glass substrate 120 because the crackmitigating layer 130 physically prevents such alignment. Alternately oradditionally, the crack mitigating layer 130 may have an engineeredmicrostructure that provides a tortuous path for crack propagation,providing an alternative path for strain energy release and minimizingor preventing crack bridging between the glass substrate 120 and film110.

In one or more embodiments, the crack mitigating layer 130 may include:porous oxides, such as SiO₂, SiO, SiO_(x), Al₂O₃; TiO₂, ZrO₂, Nb₂O₅,Ta₂O₅, GeO₂ and similar material(s) known in the art; porous versions ofthe films mentioned elsewhere herein, for example porousindium-tin-oxide, porous aluminum-zinc-oxide, or porousfluorinated-tin-oxide; porous nitrides or carbides, for example Si₃N₄,AlN, TiN, TiC; porous oxycarbides and oxy-carbo-nitrides, for example,SiC_(x)O_(y) and SiC_(x)O_(y)N_(z); porous semiconductors such as Si orGe; porous oxynitrides such as SiO_(x)N_(y), AlO_(x)N_(y), orSiAl_(x)O_(y)N_(z); porous metals such as Al, Cu, Ti, Fe, Ag, Au, andothers metals; tough or nanostructured inorganics (which may be porousor non-porous), for example, zinc oxide, certain Al alloys, Cu alloys,steels, or stabilized tetragonal zirconia; (including transformationtoughened, partially stabilized, yttria stabilized, ceria stabilized,calcia stabilized, and magnesia stabilized zirconia); zirconia-toughenedceramics (including zirconia toughened alumina); ceramic-ceramiccomposites; carbon-ceramic composites; fiber- or whisker-reinforcedceramics or glass-ceramics (for example, SiC or Si₃N₄ fiber- orwhisker-reinforced ceramics); metal-ceramic composites; porous ornon-porous hybrid organic-inorganic materials, for example,nanocomposites, polymer-ceramic composites, polymer-glass composites,fiber-reinforced polymers, carbon-nanotube- or graphene-ceramiccomposites, silsesquioxanes, polysilsesquioxanes, or “ORMOSILs”(organically modified silica or silicate), and/or a variety of porous ornon-porous polymeric materials, for example siloxanes, polysiloxanes,polyacrylates, polyacrylics, PI (polyimides), fluorinated polyimide,polyamides, PAI (polyamideimides), polycarbonates, polysulfones, PSU orPPSU (polyarylsulfones), fluoropolymers, fluoroelastomers, lactams,polycylic olefins, and similar materials, including, but not limited toPDMS (polydimethylsiloxane), PMMA (poly(methyl methacrylate)), BCB(benzocyclobutene), PEI (polyetherimide), poly(arylene ethers) such asPEEK (poly-ether-ether-ketone), PES (polyethersulfone) and PAR(polyarylate), PET (polyethylene terephthalate), PEN (polyethylenenapthalate=poly(ethylene-2,6-napthalene dicarboxylate), FEP (fluorinatedethylene propylene), PTFE (polytetrafluoroethylene), PFA (perfluroalkoxypolymer, e.g., trade names Teflon®, Neoflon®) and similar materials.Other suitable materials include modified polycarbonates, some versionsof epoxies, cyanate esters, PPS (polyphenylsulfides), polyphenylenes,polypyrrolones, polyquinoxalines, and bismaleimides. In someembodiments, suitable polyacrylates can include poly(butyl acrylate). Insome cases it will be desirable to choose the high-temperature polymericmaterials such as siloxanes, silsesquioxanes, polyimides, BCB,fluoropolymers, and others listed herein or known in the art becausethese materials will tolerate a wider range of temperatures fordeposition and/or curing of the film 110. Examples of BCB polymersinclude the Cyclotene™ resins from Dow Chemical. Examples of polyimidesand polyimide precursors include Pyralin™ resins from HD Microsystems orelectronics grade polyamic acid solution from Sigma Aldrich (cat. no.431206). The polyimides may include fluorinated or non-fluorinatedpolyimides such as those disclosed in U.S. Pat. No. 5,325,219 andrelated references, or other work known in the art such as “Preparationand Properties of a High Temperature, Flexible and Colorless ITO CoatedPolyimide Substrate”, European Polymer Journal, 43, p. 3368, 2007;“Flexible Organic Electroluminescent Devices Based onFluorine-Containing Colorless Polyimide Substrates”, Advanced Materials,14, 18, p. 1275, 2002; and “Alignment layer effects on thin liquidcrystal cells,” Appl. Phys. Lett. 92, 061102, 2008. Examples ofsilsesquioxanes include Accuglass® Spin-on-Glasses from Honeywell orFOx® Flowable Oxides from Dow Corning.

The crack mitigating layer 130 may be disposed between the film 110 andthe glass substrate 120 by a variety of methods. The crack mitigatinglayer 130 can be disposed using vacuum deposition techniques, forexample, chemical vapor deposition (e.g., plasma enhanced chemical vapordeposition), physical vapor deposition (e.g., reactive or nonreactivesputtering or laser ablation), thermal, resistive, or e-beam evaporationand/or atomic layer deposition. The crack mitigating layer 130 may alsobe disposed using liquid-based deposition techniques, for examplesol-gel coating or polymer coating methods, for example spin, spray,slot draw, slide, wire-wound rod, blade/knife, air knife, curtain,roller, gravure coating among others and other methods known in the art.

In one or more embodiments, the crack mitigating layer 130 may include aporous layer, or more specifically, a nanoporous layer. As used herein,the term “nanoporous” includes materials with traditionally-defined“pores” (e.g., openings or voids) and also includes materials that arecharacterized by a lower density or a lower elastic modulus than isexpected for fully dense materials having the same or similar chemicalcomposition. Thus, the “pores” in the nanoporous layer may take the formof columnar voids, atomic vacancies, spherical pores, intersticesbetween grains or particles, regions of low or varying density, or anyother geometry that leads to a macroscopic decrease in density orelastic modulus for the nanoporous layer. The volume fraction ofporosity can be estimated from refractive index measurements using knownmethods, for materials with nanoscale pores and no light scattering orvery low light scattering. In one or more embodiments, the volumefraction of porosity may be greater than about 5%, greater than about10%, or greater than about 20%. In some embodiments the volume fractionof porosity may be less than about 90%, or less than about 60%, topreserve mechanical durability of the nanoporous layers during handlingand end use.

The nanoporous layer may be substantially optically transparent and freeof light scattering, for example having an optical transmission haze of10% of less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less,4% or less, 3% or less, 2% or less, 1% or less and all ranges andsub-ranges therebetween. The transmission haze of the nanoporous layermay be controlled by controlling the average sizes of pores, as definedherein. Exemplary average pore sizes in the nanoporous layer may include200 nm or less, 100 nm or less, 90 nm or less, 80 nm or less, 70 nm orless, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nmor less, 10 nm or less, 5 nm or less and all ranges and sub-rangestherebetween. These pore sizes can be estimated from light scatteringmeasurements, or directly analyzed using transmission electronmicroscopy (TEM) and other known methods. The nanoporous layer of someembodiments may have a low-elastic modulus, and may serve to strengthenthe article by preventing crack bridging, or suppressing crack growth asdescribed elsewhere herein.

In other cases, the nanoporous layer may reduce the stress intensityfactor (K_(1C)) at the tip(s) of one or more cracks originating in oneof the film and the glass substrate and propagating toward the other ofthe film and the glass substrate. Without a low-elastic modulus crackmitigating layer, the stress intensity factor at the crack tips willincrease significantly as the size of a crack in the film approaches thethickness of the film, (e.g. as a crack from the film approaches theinterface with the glass substrate). This condition where the stressintensity factor at the crack tips increases favors penetration of acrack from the film into the glass substrate. Conversely, in some caseswhere a crack may be growing or propagating through a film and alow-elastic modulus crack mitigating layer, as the crack approaches theinterface between the low-elastic modulus crack mitigating layer and theglass substrate, the stress intensity factor at the crack tip decreasessubstantially. The decrease in the stress intensity factor at the cracktip is especially prominent where the crack mitigating layer has anelastic modulus that is lower than the elastic modulus of the glasssubstrate. This decrease in the stress intensity factor due to thepresence of the low-elastic modulus crack mitigating layer suppressesthe tendency for crack growth into the glass substrate, and thusincreases the overall average flexural strength of the article relativeto a similar article without the low-elastic modulus crack mitigatinglayer.

In one or more embodiments where the crack mitigating layer includes ananoporous layer, the crack mitigating layer may at least partiallydelaminate during the loading process that causes crack growth or crackformation in the film and/or the crack mitigating layer. Thisdelamination occurs at the interface between crack mitigating layer andthe glass substrate. In other embodiments, at the interface between thecrack mitigating layer and the film, the film may at least partiallydelaminate during a loading process that causes crack growth orformation in the film. Without being bound by theory, delamination orpartial delamination of the crack mitigating layer and/or film reducesthe stress concentrations in the glass substrate. Accordingly, it isbelieved that a reduction in stress concentrations in the glasssubstrate causes an increase in the load or strain level that isrequired for the glass substrate (and ultimately the article) to fail.In this manner, a crack mitigating layer that includes a nanoporouslayer prevents a decrease or increases the average flexural strength ofthe article, as compared to articles without the crack mitigating layer.

In one or more embodiments, the crack mitigating layer may cause a crackoriginating in the film or the glass substrate and entering into thecrack mitigating layer to remain in the crack mitigating layer.Alternatively or additionally, the crack mitigating layer effectivelyconfines a crack originating in one of the film and glass substratesfrom propagating into the other of such film and glass substrate. Thesebehaviors may be characterized individually or collectively as crackdeflection. The crack mitigating layer may cause cracks originating inthe film or the glass substrate and entering the crack mitigating layerto remain in the crack mitigating layer by creating favorable conditionsin which the crack deflects into and stays within the crack mitigatinglayer, instead of propagating into the glass substrate or the film. Inone or more embodiments, the crack mitigating layer may cause cracksoriginating in the film or the glass substrate and entering the crackmitigating layer to remain in the crack mitigating layer by creating aless tortuous path for crack propagation into and/or through the crackmitigating layer, instead of into the glass substrate or the film. Inone or more embodiments, the crack mitigating layer, which can include ananoporous layer, may provide a low toughness layer that exhibits a lowfracture toughness and/or a low critical strain energy release rate. Oneor more of these attributes (i.e., low fracture toughness and lowcritical strain energy release rate) may cause this crack deflectioninto the crack mitigating layer instead of through the crack mitigatinglayer into the film and/or glass substrate. For example, the crackmitigating layer 130 may exhibit a fracture toughness of about 1MPa·m^(1/2) or less, 0.75 MPa·m^(1/2) or less, 0.5 MPa·m^(1/2) or less,0.4 MPa·m^(1/2) or less, 0.3 MPa·m^(1/2) or less, 0.25 MPa·m^(1/2) orless, 0.2 MPa·m^(1/2) or less, and all ranges and sub-ranges therebetween. In other examples, the crack mitigating layer may exhibit acritical strain energy release rate that is less than 0.25 times or lessthan 0.5 times the critical strain energy release rate of the glasssubstrate. In specific embodiments, the critical strain energy releaserate of the crack mitigating layer can be less than about 0.05 kJ/m²,less than about 0.005 kJ/m², less than about 0.003 kJ/m², less thanabout 0.002 kJ/m², less than about 0.001 kJ/m², but in some embodiments,greater than about 0.0001 kJ/m² (i.e. greater than about 0.1 J/m²). Inembodiments in which the crack mitigating layer includes a nanoporouslayer, a crack originating in one of the film and the glass substratemay be deflected by the crack mitigating layer and may propagate throughthe crack mitigating layer, in a direction that is substantiallyparallel to the interface formed by the crack mitigating layer 130 andglass substrate 120 and the interface formed by the film 110 and thecrack mitigating layer 130. In such embodiments, the crack mitigatinglayer 130 provides a preferred path for crack propagation. In this way,the crack is deflected from bridging between the film and the glasssubstrate.

In one or more embodiments, the nanoporous layer may include aninorganic material. In one or more specific embodiments, the crackmitigating layer only includes a nanoporous layer and is nanoporousthroughout. The nanoporous layer may include inorganic materials andmay, alternatively, exclude organic materials. The nanoporous layer ofone or more embodiments may exhibit higher temperature tolerance,robustness to UV ozone or plasma treatments, UV transparency, robustnessto environmental aging, low outgassing in vacuum, and the like. Suchnanoporous layers may be characterized as vacuum-deposited nanoporouslayers. In addition, the use of an inorganic material providesflexibility in formation techniques. For example, such inorganicnanoporous layers may be formed by vacuum deposition (e.g. thermalevaporation, e-beam evaporation, RF sputtering, DC sputtering, chemicalvapor deposition, plasma-enhanced chemical vapor deposition, atmosphericpressure chemical vapor deposition, and the like). In instances wherethe film is also formed by vacuum deposition, both the crack mitigatinglayer and the film can be formed in the same or similar vacuumdeposition chamber or using the same or similar coating equipment.

In one or more embodiments, the crack mitigating layer may include aninorganic nanoporous layer that exhibits low intrinsic film stresses. Inspecific embodiments, such crack mitigating layers may be formed usingtechniques that control intrinsic film stresses (e.g., vacuumdeposition) in the crack mitigating layer (relative to, for example,some sol-gel coating processes). The control of intrinsic film stressesmay also enable control over other mechanical properties such asstrain-to-failure of the crack mitigating layer.

Porosity and mechanical properties of the crack mitigating layer can becontrolled using careful control of deposition methods such as a slightoverpressure of gas in the vacuum chamber, low temperature deposition,deposition rate control, and plasma and/or ion-beam energy modification.Although vapor deposition methods are commonly used, other known methodscan be used to provide a crack mitigating layer with the desiredporosity and/or mechanical properties. For example, the crack mitigatinglayer including a nanoporous layer can also be formed by wet-chemistryor sol-gel methods, such as spin coating, dip coating, slot/slitcoating, roller coating, gravure coating, and spray coating. Porositycan be introduced to wet-coated nanoporous layers by use of a poreformer (such as a block copolymer pore former) which is later dissolvedor thermally decomposed, phase separation methods, or the casting of aparticulate or nanoparticulate layer where interstices between particlesremain partially void.

In some embodiments the nanoporous layer may exhibit a similarrefractive index to either the glass substrate and/or film and/oradditional layers (as described herein), to minimize opticalinterference effects. Additionally or alternatively, the nanoporouslayer may exhibit a refractive index that is tuned to achieveanti-reflective interference effects. The refractive index of thenanoporous layer can be engineered somewhat by controlling thenanoporosity of the nanoporous layer. For example, in some cases it maybe desirable to choose a material with a relatively high refractiveindex, such as Al₂O₃, TiO₂, Nb₂O₅, Si₃N₄, or AlN, which when made into ananoporous layer with a targeted porosity level can exhibit anintermediate refractive index in the range from about 1.4 to about 1.8or a refractive index that approximates the glass substrate (e.g., inthe range from about 1.45 to about 1.6). The refractive index of thenanoporous layer can be related to the porosity level using “effectiveindex” models that are known in the art.

The thickness of the crack mitigating layer 130 may be in the range ofabout 0.01 μm to about 10 μm (10 nm to 10,000 nm) or in the range fromabout 0.04 μm to about 0.5 μm (40 nm to about 500 nm); however in somecases the film can be much thinner, for example, the crack mitigatinglayer 130 may be a single-molecule “monolayer” having a thickness ofabout 0.1 nm to about 2 nm. In one or more embodiments, the thickness ofthe crack mitigating layer 130 is in the range from about 0.02 μm toabout 10 μm, from about 0.03 μm to about 10 μm, from about 0.04 μm toabout 10 μm, from about 0.05 μm to about 10 μm, from about 0.06 μm toabout 10 μm, from about 0.07 μm to about 10 μm, from about 0.08 μm toabout 10 μm, from about 0.09 μm to about 10 μm, from about 0.1 μm toabout 10 μm, from about 0.01 μm to about 9 μm, from about 0.01 μm toabout 8 μm, from about 0.01 μm to about 7 μm, from about 0.01 μm toabout 6 μm, from about 0.01 μm to about 5 μm, from about 0.01 μm toabout 4 μm, from about 0.01 μm to about 3 μm, from about 0.01 μm toabout 2 μm, from about 0.01 μm to about 1 micron, from about 0.02 μm toabout 1 micron, from about 0.03 to about 1 μm, from about 0.04 μm toabout 0.5 μm, from about 0.05 μm to about 0.25 μm or from about 0.05 μmto about 0.15 μm.

In one or more embodiments, thicknesses of the glass substrate 120, film110 and/or crack mitigating layer 130 may be specified in relation toone another. For example, the crack mitigating layer may have athickness that is less than or equal to about 10 times the thickness ofthe film. In another example, where a film 110 has a thickness of about85 nm, the crack mitigating layer 130 may have a thickness of about 850nm or less. In yet another example, the thickness of the crackmitigating layer 130 may be in the range from about 35 nm to about 80 nmand the film 110 may have a thickness in the range from about 30 nm toabout 300 nm. In one variant, the crack mitigating layer may have athickness that is less than or equal to about 9 times, 8 times, 7 times,6 times, 5 times, 4 times, 3 times or two times the thickness of thefilm. In another variant, the thickness of the film and the thickness ofthe crack mitigating film are each less than about 10 μm, less thanabout 5 μm, less than about 2 μm, less than about 1 less than about 0.5μm, or less than about 0.2 μm. The ratio of the crack mitigating layer130 thickness to the film 110 thickness may be, in some embodiments, inthe range from about 1:1 to about 1:8, in the range from about 1:2 toabout 1:6, in the range from about 1:3 to about 1:5, or in the rangefrom about 1:3 to about 1:4. In another variant, the thickness of thecrack mitigating layer is less than about 0.1 μm and the thickness ofthe film is greater than the crack mitigating layer.

One or more embodiments of the article include a crack mitigating layer130 comprising polyimide. In such embodiments, when the crack mitigatinglayer 130 is utilized, the film 110 maintains functional properties(e.g., electrical conductivity) and the article 100 retains its averageflexural strength. In such embodiments, the film 110 may include one ormore transparent conductive oxide layers, such as indium-tin-oxidelayers. In addition, the glass substrate 120 may be strengthened, ormore specifically, chemically strengthened. In these embodiments, use ofpolyimide or other high-temperature-tolerant polymers as components ofthe crack mitigating layer may be preferred because thesehigh-temperature-tolerant polymers can withstand the sometimes harshvacuum deposition conditions of certain films, an important factor inenabling the desired film properties to be maintained.

Additionally or alternatively, the film 110 comprising indium-tin-oxideand the crack mitigating layer 130 comprising polyimide form a stack,wherein the stack has an overall low optical reflectance. For example,the overall (or total) reflectance of such a stack may be 10% or less,8% or less, 7% or less, 6.5% or less, 6% or less, 5.5% or less across avisible wavelength range from 450-650 nm, 420-680 nm, or even 400-700nm. The reflectance numbers above are quoted including the reflectancefrom one external bare (or uncoated) glass interface, as shown in theoptical reflectance simulations of FIGS. 10, 11, and 12, which isapproximately 4% reflectance from the external uncoated glass interfacealone, and for a specific embodiment where a polyimide crack mitigatinglayer 130 and an indium-tin-oxide film 110 are covered by someencapsulation or adhesive layer. Thus, the reflectance from this filmstack structure and film-glass coated interfaces alone (subtracting outthe reflectance of the external, uncoated glass interface) is less thanabout 5%, 4%, 3%, 2%, or even less than about 1.5% across a visiblewavelength range from 450-650 nm, 420-680 nm, or even 400-700 nm, whencovered by a typical encapsulant (i.e. an additional film or layer)having an encapsulant refractive index of about 1.45-1.65. In addition,the stack structure may exhibit a high optical transmittance, whichindicates both low reflectance and low absorptance, according to thegeneral relationship: Transmittance=100%−Reflectance−Absorptance. Thetransmittance values for the stack structure (when neglectingreflectance and absorptance associated with the glass substrate orencapsulant layers alone) may be greater than about 75%, 80%, 85%, 90%,95%, or even 98% across a visible wavelength range from 450-650 nm,420-680 nm, or even 400-700 nm, when covered by a typical encapsulant(i.e. an additional film or layer) having an encapsulant refractiveindex of about 1.45-1.65.

One or more embodiments of the article include a crack mitigating layer130 comprising nanoporous, vapor-deposited SiO₂. In such embodiments,when the crack mitigating layer 130 is utilized, the film 110 maintainsfunctional properties (e.g., electrical conductivity) and the article100 retains its average flexural strength, or has an improved averageflexural strength relative to a similar article comprising film 110 andglass substrate 120 without the crack mitigating layer 130. In suchembodiments, the film 110 may include one or more transparent conductiveoxide layers, such as indium-tin-oxide layers. In addition, the glasssubstrate 120 may be strengthened, or more specifically, chemicallystrengthened. In these embodiments, use of an inorganic, nanoporouscrack-mitigating layer may be utilized for some applications because ofthe temperature, vacuum, and environmental tolerance factors mentionedelsewhere herein.

Polymeric or organic-inorganic hybrid materials can be employed in thecrack mitigating layer 130 where it is desirable for the crackmitigating layer 130 to have ductile properties or to be plasticallydeformable, with or without porosity. In addition, the crack mitigatinglayer 130 may include ductile metal films such as Al or Cu.

In some embodiments a useful measure of tendency towards plasticdeformation is the elongation at break (expressed as a “%” or a “strainvalue”). In these embodiments the crack mitigating layer 130 may beductile or plastically deformable and may include material that exhibitsan elongation at break, in terms of strain value, greater than about 1%,greater than 2%, greater than 5%, or even greater than 10%. The crackmitigating layer 130 may have a higher elongation to break than the film110. Exemplary materials for use in crack mitigating layers 130 that areductile or plastically deformable include a variety of metals andpolymers, including organic-inorganic hybrids, materials listed aboveincluding, but not limited to, polyimides, PTFE(polytetrafluoroethylene), PES (polyethersulfone), PEI (polyetherimide),PPSU (polyphenylsulfone), PVDF (polyvinylidine difluoride), polyesters,and similar materials known in the art. In instances where a ductile orplastically deformable crack mitigating layer 130 is utilized, the crackmitigating layer 130 may also have a high toughness. For example, thecrack mitigating layer 130 may have a fracture toughness of 0.5MPa·m^(1/2) or greater, or in some cases 5 MPa·m^(1/2) or greater. Thecrack mitigating layer may also have a high critical strain energyrelease rate, with values as listed hereinabove.

The optical properties of the article 100 may be adjusted by varying oneor more of the properties of the film 110, crack mitigating layer 130and/or the glass substrate 120. For example, the article 100 may exhibita total reflectance of 10% or less, 8% or less, 7% or less, 6.9% orless, 6.8% or less, 6.7% or less, 6.6% or less, 6.5% or less, 6.4% orless, 6.3% or less, 6.2% or less, 6.1% or less and/or 6% or less, overthe visible wavelength range from about 400 nm to about 700 nm. Rangesmay further vary as specified hereinabove, and ranges for the filmstack/coated glass interfaces alone are listed hereinabove. In morespecific embodiments, the article 100 described herein, may exhibit alower average reflectance and greater average flexural strength thanarticles without a crack mitigating layer 130. In one or morealternative embodiments, at least two of optical properties, electricalproperties or mechanical properties of the article 100 may be adjustedby varying the thickness(es) of the glass substrate 120, film 110 and/orthe crack mitigating layer 130. Additionally or alternatively, theaverage flexural strength of the article 100 may be adjusted or improvedby modifying the thickness(es) of the glass substrate 120, film 110and/or the crack mitigating layer 130.

The article 100 may include one or more additional films disposed on theglass substrate. In one or more embodiments, the one or more additionalfilms may be disposed on the film 110 or on the opposite major surfacefrom the film. The additional film(s) may be disposed in direct contactwith the film 110. In one or more embodiments, the additional film(s)may be positioned between: 1) the glass substrate 120 and the crackmitigating layer 130; or 2) the crack mitigating layer 130 and the film110. In one or more embodiments, both the crack mitigating layer 130 andthe film 110 may be positioned between the glass substrate 120 and theadditional film(s). The additional film(s) may include a protectivelayer, an adhesive layer, a planarizing layer, an anti-splinteringlayer, an optical bonding layer, a display layer, a polarizing layer, alight-absorbing layer, reflection-modifying interference layers,scratch-resistant layers, barrier layers, passivation layers, hermeticlayers, diffusion-blocking layers and combinations thereof, and otherlayers known in the art to perform these or related functions. Examplesof suitable protective or barrier layers include layers containingSiO_(x), SiN_(y), SiO_(x)N_(y), other similar materials and combinationsthereof. Such layers can also be modified to match or complement theoptical properties of the film 110, the crack mitigating layer 130and/or the glass substrate 120. For example, the protective layer may beselected to have a similar refractive index as the crack mitigatinglayer 130, the film 110, or the glass substrate 120. It will be apparentto those of ordinary skill in the art that multiple additional film(s)with varying refractive indices and/or thicknesses can be inserted forvarious reasons. The refractive indices, thicknesses and otherproperties of the additional films (as well as the crack mitigatinglayer 130 and the film 110) may be further modified and optimized,without departing from the spirit of the disclosure. In other cases, forexample, alternate film designs can be employed where the crackmitigating layer 130 may have a higher refractive index than the film.In other cases, the crack mitigating layer 130 may be engineered to haveeven lower elastic modulus or greater ductility or plasticity than theembodiments and examples disclosed herein.

In one or more embodiments, the articles 100 described may be used ininformation display devices and/or touch-sensing devices. In one or morealternative embodiments, the article 100 may be part of a laminatestructure, for example as a glass-polymer-glass laminated safety glassto be used in automotive or aircraft windows. An exemplary polymermaterial used as an interlayer in these laminates is PVB (Polyvinylbutyral), and there are many other interlayer materials known in the artthat can be used. In addition, there are various options for thestructure of the laminated glass, which are not particularly limited.The article 100 may be curved or shaped in the final application, forexample as in an automotive windshield, sunroof, or side window. Thethickness of the article 100 can vary, for either design or mechanicalreasons; for example, the article 100 can be thicker at the edges thanat the center of the article. The article 100 may be acid polished orotherwise treated to remove or reduce the effect of surface flaws.

Another aspect of the present disclosure pertains to touch-sensingdevices including the articles described herein. In one or moreembodiments, the touch sensor device may include a glass substrate 120(which may be strengthened or not strengthened), a film 110 comprising atransparent conductive oxide and a crack mitigating layer 130. Thetransparent conductive oxide may include indium-tin-oxide,aluminum-zinc-oxide, fluorinated tin oxide, or others known in the art.In one or more embodiments, the film 110 is discontinuously disposed onthe glass substrate 120. In other words, the film 110 may be disposed ondiscrete regions of the glass substrate 120. The discrete regions withthe film form patterned or coated regions (not shown), while thediscrete regions without the film form unpatterned or uncoated regions(not shown). In one or more embodiments, the patterned or coated regionsand unpatterned or uncoated regions are formed by disposing the film 110continuously on a surface of the glass substrate 120 and thenselectively etching away the film 110 in the discrete regions so thatthere is no film 110 in those discrete regions. The film 110 may beetched away using an etchant such as HCl or FeCl₃ in aqueous solutions,such as the commercially available TE-100 etchant from Transene Co. Inone or more embodiments, the crack mitigating layer 130 is notsignificantly degraded or removed by the etchant. Alternatively, thefilm 110 may be selectively deposited onto discrete regions of a surfaceof the glass substrate 120 to form the patterned or coated regions andunpatterned or uncoated regions.

In one or more embodiments, the uncoated regions have a totalreflectance that is similar to the total reflectance of the coatedregions. In one or more specific embodiments, the unpatterned oruncoated regions have a total reflectance that differs from the totalreflectance of the patterned or coated regions by about 5% or less, 4.5%or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2.0% orless, 1.5% or less or even 1% or less across a visible wavelength in therange from about 450 nm to about 650 nm, from about 420 nm to about 680nm or even from about 400 nm to about 700 nm.

In accordance with another aspect of the present disclosure, articles100 including both a crack mitigating layer 130 and a film 110, whichmay include indium-tin-oxide or other transparent conductive oxides,exhibit resistivity that is acceptable for use of such articles in touchsensing devices. In one or more embodiments, the films 110, when presentin the articles disclosed herein, exhibit a sheet resistance of about100 ohm/square or less, 80 ohm/square or less, 50 ohm/square or less, oreven 30 ohm/square or less. In such embodiments, the film may have athickness of about 200 nm or less, 150 nm or less, 100 nm or less, 80 nmor less, 50 nm or less or even 35 nm or less. In one or more specificembodiments, such films, when present in the article, exhibit aresistivity of 10×10⁻⁴ ohm-cm or less, 8×10⁻⁴ ohm-cm or less, 5×10⁻⁴ohm-cm or less, or even 3×10⁻⁴ ohm-cm or less. Thus, the films 110, whenpresent in the articles 100 disclosed herein can favorably maintain theelectrical and optical performance expected of transparent conductiveoxide films and other such films used in touch sensor applications,including projected capacitive touch sensor devices.

The disclosure herein can also be applied to articles which havearticles that are not interactive or for display; for example, sucharticles may be used in a case in which a device has a glass front sidethat is used for display and can be interactive, and a back side thatmight be termed “decorative” in a very broad sense, meaning thatbackside can be “painted” some color, have art work or information aboutthe manufacturer, model and serial number, texturing or other features.

Another aspect of the present disclosure pertains to a method of formingan article 100. In one or more embodiments, such methods includeproviding a glass substrate 120, disposing a crack mitigating layer 130on a surface (e.g., one or more of the major surfaces 122, 124 and/orone or more minor surfaces) of the glass substrate 120, disposing a film110 on the crack mitigating layer 130, such that the crack mitigatinglayer 130 is disposed between the film 110 and the glass substrate 120.In one or more embodiments, the method includes disposing the film 110and/or the crack mitigating layer 130 via a vacuum deposition process.In particular embodiments, such vacuum deposition processes may utilizetemperatures of at least about 100° C., 200° C., 300° C., 400° C. andall ranges and sub-ranges therebetween. In some embodiments, the crackmitigating layer may be formed by wet process, as described herein. Inone or more embodiments, the method includes providing a crackmitigating layer solution that is diluted with a solvent thinner. In oneor more embodiments, the method includes diluting the crack mitigatinglayer solution in a 50:50, 40:60, 30:70 or 20:80 ratio with a solventthinner, or forming a polymer/solvent mixture comprising 30 wt %, 20 wt%, 10 wt %, 5 wt %, 2 wt %, 1 wt %, or 0.1 wt % of polymer, and allranges and sub-ranges there between. The diluted crack mitigating layermay be applied to the glass substrate by various wet process methodsknown in the art.

In one or more specific embodiments, the method includes controlling thethickness(es) of the crack mitigating layer 130 and/or the film 110.Controlling the thickness(es) of the films disclosed herein may beperformed by controlling one or more processes for forming the films sothat the films are applied having a desired or defined thickness. In aneven more specific embodiment, the method includes controlling thethickness(es) of the crack mitigating layer 130 and/or the film 110 tomaintain the average flexural strength of the glass substrate 120 and/orthe functional properties of the film 110.

In one or more embodiments, the method may include creating porosity inthe crack mitigating layer 130. The method may optionally includecontrolling the porosity of the crack mitigating layer as otherwisedescribed herein. The method may further include controlling theintrinsic film stresses of the crack mitigating layer and/or the filmthrough control of deposition and fabrication processes of the crackmitigating layer.

The method may include disposing an additional film on the glasssubstrate 120. In one or more embodiments, the method may includedisposing the additional film on the glass substrate such that theadditional film is disposed between the glass substrate 120 and thecrack mitigating layer 130, between the crack mitigating layer 130 andthe film 110 or, such that the film 110 is between the crack mitigatinglayer 130 and the additional film. Alternatively, the method may includedisposing the additional film on the opposite major surface of the glasssubstrate 120 from the surface on which the film is disposed. Theadditional film may include a protective layer, an adhesive layer, aplanarizing layer, an anti-splintering layer, an optical bonding layer,a display layer, a polarizing layer, a light-absorbing layer,reflection-modifying interference layers, scratch-resistant layers,barrier layers, passivation layers, hermetic layers, diffusion-blockinglayers, or combinations thereof.

In one or more embodiments, the method includes strengthening the glasssubstrate 120 before or after disposing the crack mitigating layer 130,film 110 and/or an additional film on the glass substrate. The glasssubstrate 120 may be strengthened chemically or otherwise. The glasssubstrate 120 may be strengthened after disposing the crack mitigatinglayer 130 on the glass substrate 120 but before disposing the film 110on the glass substrate. The glass substrate 120 may be strengthenedafter disposing the crack mitigating layer 130 and the film 110 on theglass substrate 120 but before disposing an additional film (if any) onthe glass substrate. Where no additional film is utilized, the glasssubstrate 120 may be strengthened after disposing the crack mitigatinglayer 130 and the film 110 on the glass substrate.

The following examples represent certain non-limiting embodiments of thedisclosure.

Examples 1A-1J

Examples 1A-1J include articles according to one or more embodiments ofthe present disclosure or glass substrates of the prior art. Each ofExamples 1A-1J utilized glass substrates that included a composition of61 mol %≤SiO₂≤75 mol %; 7 mol %≤Al₂O₃≤15 mol %; 0 mol %≤B₂O₃≤12 mol %; 9mol %≤Na₂O≤21 mol %; 0 mol %≤K₂O≤4 mol %; 0 mol %≤MgO≤7 mol %; 0 mol%≤CaO≤3 mol %, and 0 mol %≤SnO2≤1 mol %. The glass substrates had athickness of 0.7 mm. In Examples 1A-1E, the glass substrates werestrengthened by ion exchange to provide a surface compressive stress(CS) of about 690 MPa and a compressive depth of layer (DOL) of about 23μm. The glass substrate of Example 1F was not strengthened by ionexchange. In Examples 1G-1J, the strengthened glass substrates werestrengthened by ion exchange to provide a surface compressive stress ofabout 740 MPa and a compressive depth of layer of about 44 μm. A crackmitigating layer comprising polyimide and/or a film comprisingindium-tin-oxide were disposed on the strengthened glass substrates and(non-strengthened) glass substrates as provided below in Table 1.Examples 1A, 1E, 1F, 1G and IH are indicated as comparative because theydid not include a crack mitigating layer.

TABLE 1 Examples 1A-1J. Crack Surface CS/ Mitigating Film CompressiveLayer (indium-tin- Example Glass Substrate DOL (polyimide) oxide) 1AStrengthened 690 MPa/23 μm none None (comparative) 1B Strengthened 690MPa/23 μm 155 nm 85 nm 1C Strengthened 690 MPa/23 μm 220 nm 85 nm 1DStrengthened 690 MPa/23 μm 290 nm 85 nm 1E Strengthened 690 MPa/23 μmNone 85 nm (comparative) 1F Not — None 85 nm (comparative) strengthened1G Strengthened 740 MPa/44 μm None None (comparative) 1H Strengthened740 MPa/44 μm None 85 nm (comparative) 1I Strengthened 740 MPa/44 μm 490nm 85 nm 1J Strengthened 740 MPa/44 μm  45 nm 85 nm

For the Examples including a strengthened glass substrate (i.e.,Examples 1A-1E and 1G-1J), the ion-exchange process was carried out byimmersing the glass substrate in a molten potassium nitrate (KNO₃) baththat was heated to a temperature in the range from about 350° C. to 450°C. The glass substrates were immersed in the bath for a duration of 3-8hours to achieve the surface CS and compressive DOL provided in Table 1.After completing the ion exchange process, the glass substrates ofExamples 1A-1E and 1G-1J were cleaned in a 1-4% concentration KOHdetergent solution, supplied by Semiclean KG, having a temperature of50-70° C. The detergent solution was ultrasonically agitated at 40-110KHz. The strengthened glass substrates were then rinsed in DI water,which was also ultrasonically agitated at 40-110 KHz and thereafterdried. Example 1F was also cleaned, rinsed and dried in the same manneras Examples 1A-1E and 1G-1J. In the Examples 1B-1D, 1I, and 1J where acrack mitigating layer was utilized, the following procedure wasemployed. Prior to disposing the crack mitigating layer, thestrengthened glass substrates were then baked for 10 minutes on a hotplate at a temperature of 130° C., and then removed to cool for about 2minutes.

An aminosilane-based adhesion promoter (supplied by HD Microsystemsunder the name VM-652) was applied to the strengthened and glasssubstrates and allowed to remain in the wet state for 20 seconds. Theadhesion promoter was spun off the strengthened glass substrates, byspinning the glass substrate and the adhesion promoter applied thereonin a standard vacuum-chuck spin coater at 5000 RPM. After application ofthe adhesion promoter, a solution of polyimide (supplied by HDMicrosystems under the name PI-2555) previously diluted with a solventthinner comprising N-methyl-2-pyrrolidone (supplied by HD Microsystemsunder the name T9038/9), using various volume ratios as set out below,was applied to the strengthened glass substrates. About 1 mL of thepolymer solution was applied to each glass sample measuring 50×50 mmsquare. The strengthened glass substrates with the polyimide solutionwere then spun at 500 RPM for 3-5 seconds, followed by subsequentrotation of 500-5000 RPM for 30-90 seconds, followed by an optionalfinal rotation step at 5000 RPM for 15 seconds, to obtain the desiredthickness and/or concentration of the crack mitigating layer. Example 1Bhad a polyimide thickness of 155 nm and was prepared using polyimidesolution diluted in a 30:70 ratio with the solvent thinner and was spunfirst at a rotation of 500 RPM for 3 seconds, followed by a subsequentrotation at 4000 RPM for 60 seconds. Example 1C had a polyimidethickness of 220 nm and was prepared using polyimide solution diluted ina 30:70 ratio with the solvent thinner and was spun first at a rotationof 500 RPM for 3 seconds, followed by a subsequent rotation at 1500 RPMfor 90 seconds. Example 1D had a polyimide thickness of 290 nm and wasprepared using polyimide solution diluted in a 40:60 ratio with thesolvent thinner and was spun first at a rotation of 500 RPM for 3seconds, followed by a subsequent rotation at 1000 RPM for 90 seconds.For examples 1B-1D, the polymer solutions were applied and spin coatedon the glass substrates when the solutions were at a temperature ofabout 15° C., which tends to slow the evaporation of the solvent andyield somewhat thinner films than with a higher temperature solution.Example 1I had a polyimide thickness of 490 nm and was prepared usingpolyimide solution diluted in a 50:50 ratio with the solvent thinner andwas spun first at a rotation of 500 RPM for 5 seconds, followed by asubsequent rotation at 1500 RPM for 45 seconds, followed by a finalrotation at 5000 RPM for 15 seconds. Example 1J had a polyimidethickness of 45 nm and was prepared using polyimide solution diluted ina 20:80 ratio with the solvent thinner and was spun first at a rotationof 500 RPM for 5 seconds, followed by a subsequent rotation at 2000 RPMfor 30 seconds, followed by a final rotation at 5000 RPM for 15 seconds.For examples 1I and 1J, the polymer solutions were allowed toequilibrate at room temperature (i.e., about 25° C.) for at least onehour before applying and spin coating the solutions on the glasssubstrates.

Immediately after the spin coating steps as outline above, the Examplescontaining a crack mitigating layer were then dried and baked on a hotplate at a temperature of 130° C. for 2-3 minutes and then placed in anN₂ curing oven (supplied by YES) operating at a pressure of 280 torr andcured at a temperature of 240° C. for 90 minutes. Based on known dataand information obtained by testing, the resulting crack mitigatinglayer had an elastic modulus of about 2.5 GPa to about 10 GPa and anelongation to break of about 10% after curing.

An indium-tin-oxide-containing film was applied to the Examples, asindicated in Table 1. The indium-tin-oxide film was sputtered from anoxide target, using a system supplied by KDF, under the name model 903i.The sputtering target was also supplied by KDF and included SnO₂ andIn₂O₃ present at a ratio of 10:90 by weight. The film was sputtered at apressure of 10 mTorr in the presence of oxygen flowed at a rate of about0.5 sccm and argon flowed at a rate of 30 sccm, with DC power suppliedat 600 W. After the film was disposed, as indicated in Table 1, theExamples were annealed at a temperature of about 200° C. for 60 minutesin air. For the Examples which did not include a crack-mitigating film(i.e., Examples 1E, 1F, and 1H), the glass substrate was pre-treated,before deposition of the film using a plasma cleaning step in the sameKDF system, where the plasma cleaning step employed 15 mTorr pressure,50 sccm of Argon flow, 5 sccm of oxygen flow, and 400 W of RF power for1 minute.

To demonstrate the retention of average flexural strength of thearticles and strengthened glass substrates of Examples 1A-1J, thearticles and glass substrates were tested using ring-on-ring load tofailure testing, as shown in FIG. 5. For ring-on-ring load to failuretesting, Examples 1B-1F and 1H-1J (with the film and/or crack mitigatinglayer) were tested with the side with the film and/or crack mitigatinglayer in tension. For Examples 1A and 1G (without a film or crackmitigating layer), one side of the strengthened glass substrate wassimilarly in tension. The ring-on-ring load to failure testingparameters included a contact radius of 1.6 mm, a cross-head speed of1.2 mm/minute, a load ring diameter of 0.5 inches, and a support ringdiameter of 1 inch. Before testing, an adhesive film was placed on bothsides of the articles and strengthened glass substrates to containbroken glass shards.

As illustrated in FIG. 5, the addition of a crack mitigating layerincluding polyimide, having a thickness in the range from about 45 nm toabout 490 nm, resulted in articles that retained about the same averageflexural strength as glass substrates without a crack mitigating layeror film. Moreover, the articles with a crack mitigating layer exhibitedgreater average flexural strength than the strengthened andnon-strengthened glass substrates with only a film. For comparison, thestrengthened and non-strengthened glass substrates with only a filmdisposed thereon (i.e., Examples 1E, 1F and 1H) exhibited a substantialreduction in the average flexural strength.

Examples 2A-2D

Each of Examples 2A-2D utilized glass substrates that included acomposition of 61 mol %≤SiO₂≤75 mol %; 7 mol %≤Al₂O₃≤15 mol %; 0 mol%≤B₂O₃≤12 mol %; 9 mol %≤Na₂O≤21 mol %; 0 mol %≤K₂O≤4 mol %; 0 mol%≤MgO≤7 mol %; 0 mol %≤CaO≤3 mol %, and 0 mol %≤SnO2≤1 mol %. The glasssubstrates had a thickness of 0.7 mm and were strengthened by ionexchange and prepared for combination with a crack mitigating layerand/or film, using the same processes as described with reference toExamples 1A-1J. The strengthened glass substrates of Examples 2A-2D hada surface compressive stress (CS) of about 776 MPa and a compressivedepth of layer (DOL) of about 41.4 μm. A crack mitigating layercomprising polyimide and a film comprising indium-tin-oxide weredisposed on the strengthened glass substrates as provided below in Table2, using the methods described with reference to Examples 1A-1J toprovide the articles of Examples 2A-2D. An adhesion promoter wasutilized in the same manner as Examples 1B-1D, 1I, and 1J. Example 2Ahad a polyimide thickness of 250 nm and was prepared using polyimidesolution diluted in a 30:70 volume ratio with the solvent thinner andwas spun first at a rotation of 500 RPM for 3 seconds, followed by asubsequent rotation at 4000 RPM for 60 seconds. Example 2B had apolyimide thickness of 90 nm and was prepared using polyimide solutiondiluted in a 20:80 volume ratio with the solvent thinner and was spunfirst at a rotation of 500 RPM for 3 seconds, followed by a subsequentrotation at 4000 RPM for 60 secondsonds. For examples 2A and 2B, thepolymer solutions were allowed to equilibrate at room temperature (˜25C) for at least one hour before applying and spin coating the solutionson the glass substrates. Drying, baking and curing for thesepolyimide-coated samples was carried out in the same manner as examples1B-1D, 1I, and 1J. Examples 2C and 2D are indicated as comparativebecause they did not include a crack mitigating layer.

TABLE 2 Examples 2A-2D. Crack mitigating Film Example layer (polyimide)(indium-tin-oxide) 2A 250 nm 85 nm 2B  90 nm 85 nm 2C (comparative) None85 nm 2D (comparative) None None

For ball drop height-to-failure testing, the articles of Examples 2A-2C(with the film and/or crack mitigating layer) were tested with the sidewith the film and/or crack mitigating layer in tension. For Example 2D,without a film or crack mitigating layer, one side of the strengthenedglass substrate was similarly in tension. A steel ball having a weightof 128 g and diameter of 31.75 mm was utilized. The articles and thestrengthened glass substrate each had a size of 50 mm×50 mm and weresupported at each edge. Before testing, an adhesive film was placed onboth sides of the articles and the strengthened glass substrate tocontain broken glass shards.

As illustrated in FIG. 6, the articles of Examples 2A and 2B exhibitedthe same or similar average flexural strength using ball-drop height tofailure testing as the strengthened glass substrate of Example 2D,indicating that the articles including a crack mitigating layer retainedtheir respective average flexural strength, while the articles with onlya film (and no crack mitigating layer) (i.e., Example 2C) exhibited asignificant reduction in or lower level average flexural strength.

Examples 3A-3C

Examples 3A-3C are prophetic examples that are illustrated in FIGS. 7-9,with related modeled optical reflectance data shown in FIGS. 10-12.Examples 3A and 3B correlate to Examples 4C and 4E, respectively, whichare discussed below. Example 3A-3C include articles 300, 310, 320 eachincluding a glass substrate 302, 312, 322, a crack mitigating layer 304,314, 324 including polyimide disposed on the glass substrate 302, 312,322 and a film 306, 316, 326 including indium-tin-oxide disposed on theglass substrate 302, 312, 322 such that the crack mitigating layer isbetween the glass substrate and the film. In each of Examples 3A-3C, theglass substrates have a thickness in the range from about 0.2 mm toabout 2.0 mm. Example 3A includes a crack mitigating layer 304 having athickness of 74 nm and a film 306 having a thickness of 115 nm. Example3B includes a crack mitigating layer 314 having a thickness of 85 nm anda film 316 having a thickness of 23 nm. Example 3C includes a crackmitigating layer 324 having a thickness of 64 nm and a film 326 having athickness of 115 nm. Example 3C includes an additional film 328including SiO_(x)N_(y), which functions as a protective layer, disposedbetween the crack mitigating layer 324 and the film 326. The additionalfilm 328 has a thickness of 10 nm. In Examples 3A-3C, the glasssubstrates 302, 312, 322 have a refractive index in the range from about1.45-1.55, the crack mitigating layers 304, 314, 324 have a refractiveindex in the range from about 1.6-1.75 and the films 306, 316, 326 havea refractive index in the range from about 1.8-2.2. In Example 3C, theadditional film 328 including SiOxNy has a refractive index similar tothe refractive index of the crack mitigating layer 324. Each of Examples3A-3C may include a second additional film (illustrated in FIGS. 10, 11and 12) that may include an adhesive, which will be more fully describedin Modeled Example 4.

In each of the articles 300, 310, 320, the thicknesses of the crackmitigating layer and the film were optimized to simultaneously achievegood optical properties and good mechanical properties. The foregoingexamples illustrate that the thickness range of crack mitigating layersand films used in the articles 300, 310, and 320 are effective to retainhigh average flexural strength for the article, while Modeled Examples4C and 4E (described below) illustrate that the articles 300, 310, and320 simultaneously achieve low optical reflectance. Optimization may beachieved by controlling or adjusting one or more process parametersdiscussed with reference to Examples 1A-1J.

Modeled Example 4

Examples 4C and 4E and Comparative Examples 4A, 4B, 4D and 4F wereoptically modeled using the following information in Table 3. Examples4C and 4E correlate to Examples 3A and 3B.

TABLE 3 Refractive index (n,k) values versus wavelength (WL) used in theoptical modeling designs, which are illustrated by FIGS. 10-12. CrackMitigating Layer Film Glass Substrate Additional Film WL n k WL n k WL nk WL n k 350 1.781 0.000 350 2.28 0.03 300 1.532 0.000 250 1.578 0.000400 1.742 0.000 400 2.2 0.005 450 1.517 0.000 300 1.553 0.000 450 1.7190.000 450 2.15 0.003 550 1.512 0.000 350 1.539 0.000 500 1.703 0.000 5002.11 0.003 700 1.507 0.000 400 1.531 0.000 550 1.693 0.000 550 2.070.003 1200 1.497 0.000 450 1.525 0.000 600 1.686 0.000 600 2.04 0.0030.000 500 1.521 0.000 650 1.680 0.000 650 2.015 0.005 550 1.519 0.000700 1.676 0.000 700 1.995 0.007 600 1.516 0.000 750 1.673 0.000 7501.975 0.01 650 1.515 0.000 850 1.670 0.000 850 1.94 0.02 700 1.513 0.000950 1.668 0.000 950 1.9 0.03 750 1.512 0.000 1150 1.84 0.05 800 1.5110.000 850 1.510 0.000 900 1.509 0.000 950 1.508 0.000 1000 1.508 0.000

The articles of Comparative Examples 4A and 4B were modeled using aglass substrate having a thickness of 1.0 mm and are illustrated in FIG.10. In modeled Comparative Example 4A, a film having a thickness of 100nm is disposed on the glass substrate and an additional film disposed onthe film, such that the film is disposed between the glass substrate andthe additional film, as illustrated in FIG. 10. In Comparative Example4B, the model included the additional film being disposed on the glasssubstrate without an intervening film, as also illustrated in FIG. 10.The additional film of Examples 4A and 4B includes an adhesive havingrefractive index of about 1.52. In the optical model, the additionalfilm/adhesive layer was treated as being “very thick”, meaning itrepresents the exit ambient medium in the optical model, where air isthe input ambient medium. This represents a practical case wherereflectance from the distant back surface of the adhesive are notincluded in the model, because this back surface of the adhesive layeris laminated to additional light-absorbing structures such as polarizinglayers, display layers, and device layers that absorb or scattersubstantially all of the light that transmits into the adhesive layer.The adhesive represents one or more of a protective layer, a planarizinglayer, an anti-splinter layer, or an optical bonding layer and otherlayers disclosed herein with reference to the additional film. Asillustrated in FIG. 10, the presence of a high refractive index film,such as indium-tin-oxide, without a properly designed layer structure orcrack mitigating layer, typically causes a significant increase inreflectance in the article, over the visible spectrum.

The articles of Example 4C and Example 4D were modeled using a glasssubstrate having a thickness of 1.0 mm and are illustrated in FIG. 11.In modeled Example 4C, a crack mitigating layer having a thickness of 74nm and including polyimide is disposed on a surface of the glasssubstrate, a film comprising indium-tin-oxide and having a thickness of115 nm is disposed on the crack mitigating layer and an additional filmis disposed on the film. As illustrated in FIG. 11, the crack mitigatinglayer is disposed between the glass substrate and the film, and the filmis disposed between the crack mitigating layer and the additional film.In Example 4D, the modeled article is identical to the modeled articleof Example 4C except no film is included, as illustrated in FIG. 11. Theadditional film of Example 4C and Example 4D includes an adhesive havingrefractive index of about 1.52. The adhesive is also characterized asbeing “very thick”. The adhesive represents one or more of a protectivelayer, a planarizing layer, an anti-splinter layer, or an opticalbonding layer and other layers disclosed herein with reference to theadditional film. Such layers may be commonly used in touch screendevices. As illustrated in FIG. 11, the reflectance of an article withand without a film is similar over a majority of the visible spectrum.Accordingly, when compared to Comparative Example 4A, which showed thepresence of a film significantly increasing the reflectance of anarticle without a crack mitigating layer, the crack mitigating layerabates any increase or variation of reflectance otherwise caused by thepresence of the film. In addition, the article including a glasssubstrate, a film and a crack mitigating layer exhibits a totalreflectance that is substantially similar to, that is, within 5%, 4.5%,4%, 3.5%, 3%, 2.5%, 2%, 1.5% or even 1% of the reflectance of the samearticle without the film (which may still include the crack-mitigatinglayer), across the visible wavelength range such as from about 450 toabout 650 nm, from about 420 nm to about 680 nm or even from about 400nm to about 700 nm.

The total reflectance illustrated in FIG. 11 for both of the articles ofExamples 4C and 4D (i.e., an article with and an article without a film)can be used to demonstrate the contrast between patterned or coatedregions (i.e., regions with a film comprising a transparent conductiveoxide) and non-patterned or uncoated regions (i.e., regions without afilm) in a touch sensor. The touch sensor pattern simulated by Examples4C and 4D (using the refractive index values provided in Table 3) islargely “invisible” due to the less than about 1.5% change in absolutereflectance level between the patterned or coated region (containing thefilm) and the unpatterned or uncoated region (containing no film) in awavelength range from 450-650 nm. The articles of Examples 4C and 4Dalso have a low absolute reflectance level, with total reflectance lessthan about 6% over this same wavelength range. About 4% of the totalreflectance comes from the front (uncoated) glass interface with air andless than 2% of the total reflectance comes from the coated side of theglass substrate (i.e., the crack mitigating layer, film and adhesiveinterfaces).

The articles of Example 4E and Comparative Example 4F were modeled inthe same manner as Example 4C and Comparative Example 4D, respectively;however the crack mitigating layer (comprising polyimide) had athickness of 85 nm and the film (comprising indium-tin-oxide) had athickness of 23 nm. Example 4E included a glass substrate, a crackmitigating layer disposed on the glass substrate, a film disposed on thecrack mitigating layer and an additional film disposed on the film.Comparative Example 4F is identical to Example 4E except it did notinclude the film. As illustrated in FIG. 12, the total reflectance of aglass-film substrate with and without a film is similar over a majorityof the visible spectrum. Accordingly, when compared to ComparativeExample 4A, which showed the presence of a film significantly increasingthe total reflectance of the article without a crack mitigating layer,the presence of a crack mitigating layer abates any increase orvariation of reflectance otherwise caused by the presence of a film. Inother words, an article including a glass substrate, a film and a crackmitigating layer exhibits a total reflectance that is substantiallysimilar to, that is, within 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, oreven 1% of the same article without a film.

Based on Example 3 and modeled Example 4, the articles disclosed hereinmay have a low absolute reflectance and a small change in reflectance(e.g. <1.5%) between regions containing a film and regions notcontaining a film, rendering a patterned touch sensor largely“invisible”, as shown in FIGS. 11 and 12.

Refractive index values for the films and glass substrates used in theoptical modeling of Example 4 were derived from experimental films,optical reflectometry, and estimates known in the literature. It will beapparent to those of ordinary skill in the art that these refractiveindex values can be modified based on material and process choices,requiring a complementary modification to the optimal film thicknessesspecified here. In addition, it will be apparent to those of ordinaryskill in the art that small modifications of the index values in Table 4can be achieved through material and process changes, without departingfrom the spirit of the disclosure. Likewise, small changes in the filmand substrate thicknesses and design can be utilized without departingfrom the spirit of the disclosure. Further, the crack mitigating layersin Example 3 and modeled Example 4 can be chosen to comprise additionalmaterials having similar refractive indices, and in some cases may notinclude polyimide. For example, the crack mitigating layers in Examples3 and 4 may comprise nanoporous inorganic layers, alternative polymermaterials, or other materials mentioned elsewhere herein.

Example 5: Nanoporous Crack Mitigating Layer

Examples 5A-5G were made by providing 0.7 mm thick ion-exchangestrengthened aluminosilicate glass substrates. The glass substrateincluded a composition of 61 mol %≤SiO₂≤75 mol %; 7 mol %≤Al₂O₃≤15 mol%; 0 mol %≤B₂O₃≤12 mol %; 9 mol %≤Na₂O≤21 mol %; 0 mol %≤K₂O≤4 mol %; 0mol %≤MgO≤7 mol %; 0 mol %≤CaO≤3 mol %, and 0 mol %≤SnO2≤1 mol %. Theglass substrates were ion-exchanged in a KNO₃ molten salt bath having atemperature of about 350-450° C. for 3-8 hours. The ion-exchanged glasssubstrates had a compressive stress of about 687 MPa and an ion-exchangedepth of layer of about 24 microns. The glass substrates were thencleaned in a KOH detergent solution (1-4% Semiclean KG), having atemperature of about 50-70° C. with ultrasonic agitation at 40-110 KHz,rinsed in DI water with ultrasonics in the same frequency range, anddried.

The glass substrate of Example 5A was left bare, with no layers or filmsdisposed thereon. A nanoporous SiO₂ layer was deposited on each of theglass substrates of Examples 5B, 5C, 5F and 5G using resistive thermalevaporation of a SiO precursor material at a deposition rate of 5angstroms/second, a deposition pressure of 7.3×10⁻⁴ Torr, an oxygen flowrate of 100 sccm, an argon flow rate of 100 sccm, and a substratetemperature of initially about 25° C., which increased up to about 50°C. during deposition, due to the heat generated by the depositionprocess. The resulting nanoporous SiO₂ layer had a refractive index of1.38 at 550 nm wavelength which leads to an estimated porosity of 21%.The nanoporous SiO₂ layer was measured to have an elastic modulus of 20GPa using nanoindentation. Examples 5B and 5F included a nanoporous SiO₂layer having a thickness of about 200 nm and Examples 5C and 5G includeda nanoporous SiO₂ layer having a thickness of about 500 nm.

The glass substrates of Example 5D-5E (which did not include ananoporous layer) and Examples 5F and 5G (which each included ananoporous layer) were further coated with an indium-tin-oxide (ITO)film having a thickness of about 100 nm. The ITO films were formed usinga sputtering process and a KDF, model 903i, ITO coating system. Asputtering target of SnO2:In2O3=10:90 (by weight), also supplied by KDFwas utilized. The ITO films were sputtered at a pressure of 15 mtorrwith 5 sccm flow of 90:10 mixed Ar:O2, 95 sccm Ar flow, and 1000 W DCpower. After deposition, Examples 5E-5G were annealed at 200 C for 60min in air. Example 5D was not annealed. Table 5 summarizes theattributes and processing of Examples 5A-5G.

TABLE 5 Examples 5A-5G. Nanoporous SiO₂ Layer ITO Film Annealing ExampleThickness Thickness Temperature Annealing Time Example 5A None None N/AN/A (comparative) Example 5B 200 nm None N/A N/A (comparative) Example5C 500 nm None N/A N/A (comparative) Example 5D None 100 nm None N/A(comparative) Example 5E None 100 nm 200° C. 60 min (comparative)Example 5F 200 nm 100 nm 200° C. 60 min Example 5G 500 nm 100 nm 200° C.60 min

The average flexural strength of Examples 5A-5G was evaluated in thesame manner as Examples 1A-1J. As shown in FIGS. 13 and 14, Examples 5Fand 5G (which each included a vapor-deposited nanoporous SiO₂ layerdisposed between the glass substrate and the ITO film) exhibitedimproved strength over Examples 5D and 5E (which included only an ITOfilm). Example 5D and 5E also exhibited a substantial reduction in theaverage flexural strength over Example 5A (which was a bare glasssubstrate). Examples 5B and 5C, which included no ITO film exhibitedabout the same average flexural strength as Example 5A, indicating thenanoporous SiO₂ layer did not degrade the strength of the glasssubstrate.

Examples 5D, which included 100 nm ITO film alone and was annealed,lowered the Weibull characteristic strength of the article to about 106kgf. The addition of the 200-500 nm nanoporous SiO₂ layer between theglass substrate and 100 nm ITO film (with the same annealing cycle), inExamples 5F and 5G, increased the characteristic flexural strength to175-183 kgf.

In experimental screening, the ITO films deposited on top of thenanoporous SiO₂ layers exhibited comparable resistivity levels as theITO films deposited directly on the glass substrate (with no interveningnanoporous SiO₂ layer). Sheet resistance ranged from 35-95 ohms/squarefor Examples 5D-5G (which corresponds to resistivity less than about10×10⁻⁴ ohm-cm).

Example 6: Polymeric Crack Mitigating Layer with Aluminum OxynitrideFilm

Examples 6A-6F were made by providing 1.0 mm thick ion-exchangestrengthened aluminosilicate glass substrates. The glass substrateincluded a composition of 61 mol %≤SiO₂≤75 mol %; 7 mol %≤Al₂O₃≤15 mol%; 0 mol %≤B₂O₃≤12 mol %; 9 mol %≤Na₂O≤21 mol %; 0 mol %≤K₂O≤4 mol %; 0mol %≤MgO≤7 mol %; 0 mol %≤CaO≤3 mol %, and 0 mol %≤SnO2≤1 mol %. Theglass substrates were ion-exchanged in a KNO₃ molten salt bath having atemperature of about 350-450° C. for 3-8 hours to provide strengthenedglass substrates. The strengthened glass substrates had a compressivestress of about 885 MPa and an ion-exchange depth of layer of about 42microns. The strengthened glass substrates were then cleaned in a KOHdetergent solution (1-4% Semiclean KG), having a temperature of about50-70° C. with ultrasonic agitation at 40-110 KHz, rinsed in DI waterwith ultrasonics in the same frequency range, and dried.

The strengthened glass substrate of Comparative Example 6A was leftbare, with no layers or films disposed thereon. A AlO_(x)N_(y) filmhaving a thickness of about 2000 nm was disposed on the strengthenedglass substrate of Comparative Example 6B, with no crack mitigatinglayer disposed between the AlO_(x)N_(y) film and the glass substrate. Acrack mitigating layer including polyimide was disposed on the glasssubstrates of Examples 6C-6D and a crack mitigating layer includingpolyetherimide was disposed on the glass substrates of Examples 6E-6F.The crack mitigating layer of Examples 6C-6F had varying thickness assummarized in Table 6. An AlO_(x)N_(y) film having a thickness of 2000nm was disposed on the crack mitigating layer of each of Examples 6C-6F.The AlO_(x)N_(y) films were disposed on the crack mitigating layer ofExamples 6C-6F in the same manner as Comparative Example 6B.

In Examples 6C-6F the following procedure was used to form the crackmitigating layers. Prior to disposing the crack mitigating layer, thestrengthened glass substrates were baked for 10 minutes on a hot plateat a temperature of about 130° C., and then removed to cool for about 2minutes. An aminosilane-based adhesion promoter (supplied by HDMicrosystems under the name VM-652) was applied to one major surface ofthe strengthened glass substrates and allowed to remain in the wet statefor 20 seconds. The adhesion promoter was spun off the strengthenedglass substrates, by spinning the glass substrate with the adhesionpromoter applied thereon in a standard vacuum-chuck spin coater at 5000RPM. After application of the adhesion promoter, Examples 6C and 6D werecombined with a solution of polyimide (supplied by HD Microsystems underthe name PI-2555). The polyimide solution was in some cases diluted witha thinner comprising N-methyl-2-pyrrolidone (NMP, supplied by HDMicrosystems under the name T9038/9), using volume ratios as set outbelow, and was applied to the strengthened glass substrates of Examples6C and 6D. About 1 mL of the polymer solution was applied to each glasssample measuring 50×50 mm square. The strengthened glass substrates withthe polyimide solution were then spun at 500 RPM for 3 seconds, followedby subsequent rotation of 1000-3000 RPM for 45 seconds to obtain thedesired thickness and/or concentration of the crack mitigating layer.Example 6C had a polyimide thickness of 970 nm and was prepared usingpolyimide solution diluted in a 60:40 ratio with the solvent thinner andwas spun first at a rotation of 500 RPM for 3 seconds, followed by asubsequent rotation of 2000 RPM for 45 seconds. Example 6D had apolyimide thickness of 4800 nm and was prepared using polyimide solutionthat was not diluted with the solvent thinner and was spun first at arotation of 500 RPM for 3 seconds, followed by a subsequent rotation of1500 RPM for 45 seconds.

Examples 6E and 6F were prepared similarly, except that a polyetherimide(PEI) (supplied as pellets by Aldrich under product no. 700193) solutionwas utilized. The PEI was dissolved in the same solvent thinner as usedin Examples 6C and 6D to provide a solution with a PEI concentration ofbetween 5-20 wt % and were spin-coated at speeds of 5000 RPM for 30seconds to obtain the desired thickness and/or concentration of thecrack mitigating layer. Example 6E had a PEI thickness of 185 nm and wasprepared using a 5 wt % PEI solution, with the remainder comprising thesolvent thinner, and was spun at a subsequent rotation of 5000 RPM for30 seconds. Example 6F had a PEI thickness of 4000 nm and was preparedusing a 20 wt % PEI solution, with the remainder comprising the solventthinner, and was spun at a subsequent rotation of 5000 RPM for 30seconds.

Examples 6C-6F were then baked on a hot plate at a temperature of 130°C. for 2-3 minutes and then placed in an N₂ curing oven (supplied byYES) operating at a pressure of 280 torr and cured at a temperature of240° C. for 90 minutes.

The AlO_(x)N_(y) films were then deposited either onto bare glass (Comp.Example 6B) or onto a crack mitigating layer (Examples 6C-6F) by DCreactive sputtering from an aluminum target, using a vacuum chamber at apressure of about 0.75 mTorr in the presence of argon flowed at a rateof 115 sccm, nitrogen flowed at a rate of 50 sccm and oxygen flowed at arate of 2 sccm. DC power was supplied at 4000 W. The AlO_(x)N_(y) filmwas formed at a deposition rate of about 70 angstroms/minute. Table 6summarizes the attributes of Examples 6A-6F.

TABLE 6 Examples 6A-6F. Crack Crack Mitigating Mitigating AlO_(x)N_(y)Weibull Layer Layer Film characteristic Example Material ThicknessThickness strength Example 6A None N/A None 677 kgf (comparative)Example 6B None N/A 2000 nm 153 kgf (comparative) Example 6C Polyimide 970 nm 2000 nm 208 kgf Example 6D Polyimide 4800 nm 2000 nm 636 kgfExample 6E Polyetherimide  185 nm 2000 nm 252 kgf Example 6FPolyetherimide 4000 nm 2000 nm 660 kgf

The average flexural strength of Examples 6A-6F was evaluated inring-on-ring strength testing in the same manner as Examples 1A-1J. Asshown in FIGS. 15 and 16, Examples 6C-6F (which each included polymericcrack mitigating layers) all exhibited improved average flexuralstrength (reported in terms of ring-on-ring load to failure) whencompared to Comparative Example 6B, which included an AlO_(x)N_(y) filmdisposed directly onto a glass substrate with no intervening crackmitigating layer. In addition, Examples 6D and 6F, which included crackmitigating layers having a thickness of 4800 nm and 4000 nm,respectively, exhibited substantially the same or statisticallyoverlapping average flexural strength as the original uncoated glasssubstrates (Comp. Example 6A). Comparative Example 6B, which included a2000 nm AlO_(x)N_(y) film coated directly onto a glass substrate,lowered the Weibull characteristic strength of the coated glass articleto about 153 kgf, compared to a characteristic strength of about 677 kgffor Comparative Example 6A (i.e., the uncoated ‘control’ glass sample).In comparison, as shown in Table 6, Example 6C had a characteristicstrength of about 208 kgf, Example 6D had a characteristic strength ofabout 636 kgf, Ex.ample. 6E had a characteristic strength of about 252kgf, and Example 6F had a characteristic strength of about 660 kgf. Acomparison of Comparative Example 6B with Examples 6C-6F demonstratesthat the crack mitigating layer substantially improved the averageflexural strength of the articles of Examples 6C and 6F and the articlesof Examples 6C-6F have improved average flexural strength as compared toarticles that include the same glass substrate and the same film, but nocrack mitigating layer (e.g., Comparative Example 6B).

Example 7: Nanoporous Inorganic Crack Mitigating Layer with AluminumOxynitride Film

Examples 7A-7B were made by providing 1.0 mm thick ion-exchangestrengthened aluminosilicate glass substrates. The glass substrateincluded a composition of 61 mol %≤SiO₂≤75 mol %; 7 mol %≤Al₂O₃≤15 mol%; 0 mol %≤B₂O₃≤12 mol %; 9 mol %≤Na₂O≤21 mol %; 0 mol %≤K₂O≤4 mol %; 0mol %≤MgO≤7 mol %; 0 mol %≤CaO≤3 mol %, and 0 mol %≤SnO2≤1 mol %. Theglass substrates were ion-exchanged in a KNO₃ molten salt bath having atemperature of about 350-450° C. for 3-8 hours to provide strengthenedglass substrates. The strengthened glass substrates had a compressivestress of about 885 MPa and an ion-exchange depth of layer of about 42microns. The glass substrates were then cleaned in a KOH detergentsolution (1-4% Semiclean KG), having a temperature of about 50-70° C.with ultrasonic agitation at 40-110 KHz, rinsed in DI water withultrasonics in the same frequency range, and dried.

Five glass substrates of Comparative Example 7A were left bare, with nolayers or films disposed thereon. A nanoporous SiO₂ layer was depositedon five glass substrates of Example 7B in a vacuum chamber usingresistive thermal evaporation of a SiO precursor material at adeposition rate of 5 angstroms/second, a deposition pressure of 9.0×10⁻⁴Torr, an oxygen flow rate of 150 sccm, an argon flow rate of 100 sccm,and a substrate temperature of initially about 25° C., which increasedup to about 50° C. during deposition, due to the heat generated by thedeposition process. The five samples of Example 7B were then furthercoated with 2000 nm thick AlO_(x)N_(y) films by DC reactive sputteringfrom an aluminum target at a pressure of about 0.75 mTorr in thepresence of argon flowed at a rate of 115 sccm, nitrogen flowed at arate of 50 sccm and oxygen flowed at a rate of 4 sccm. DC power wassupplied at 4000 W. The AlO_(x)N_(y) film was formed at a depositionrate of about 70 angstroms/minute. Table 7 summarizes the attributes andaverage strength values of Examples 7A-7B. As can be seen in Table 7,the average strength of the uncoated glass samples (Comparative Example7A) from this set was about 330 kgf, in this case calculated as a meanvalue of the five tested samples in terms of RoR load to failure. Theaverage strength of the samples of Example 7B was about 391 kgf.Considering the standard deviations of the average strength values, oneof ordinary skill in the art can readily understand that the strengthdistributions of these two samples sets (Comparative Example 7A andExample 7B) are statistically similar, or substantially the same.Weibull distribution analysis yields a similar statistical conclusion.As illustrated by Comparative Example 6B, similar 2000 nm thickAlO_(x)N_(y) films disposed directly onto similar glass substratesyielded RoR average load to failure values of about 140-160 kgf. Thus,the crack mitigating layer of Example 7B led to a substantialimprovement in the coated glass strength, relative to the same orsubstantially identical articles made without the crack mitigatinglayer.

TABLE 7 Examples 7A-7B. Nanoporous Average Strength Std. SiO₂AlO_(x)N_(y) (Mean Load Deviation Layer Film to Failure of Load toExample Thickness Thickness in RoR, kgf) Failure, kgf Example 7A NoneNone 330 28.1 (comparative) Example 7B 2000 nm 2000 nm 391 71.5

While the disclosure has been described with respect to a limited numberof embodiments for the purpose of illustration, those skilled in theart, having benefit of this disclosure, will appreciate that otherembodiments can be devised which do not depart from the scope of thedisclosure as disclosed herein. Accordingly, various modifications,adaptations and alternatives may occur to one skilled in the art withoutdeparting from the spirit and scope of the present disclosure.

We claim:
 1. An article, comprising: a substrate having a thickness fromabout 250 μm to about 2000 μm and opposing major surfaces including afirst major surface and a second major surface; a crack mitigating layerdisposed on and directly in contact with the first major surface of thesubstrate, wherein the crack mitigating layer has a thickness from about0.01 μm to about 10 μm; and a first film disposed on the crackmitigating layer having a thickness from about 0.01 μm to about 20 μm,wherein an average strain-to-failure of the substrate is 0.5% orgreater, as measured with the crack mitigating layer disposed on anddirectly in contact with the first major surface of the substrate andthe first film disposed on the crack mitigating layer.
 2. The articleaccording to claim 1, wherein the crack mitigating layer has a modulusthat is less than a modulus of the first film and a modulus of thesubstrate and a thickness from about 0.01 μm to less than 0.1 μm.
 3. Thearticle according to claim 1, wherein the crack mitigating layercomprises a porous or non-porous polymeric material.
 4. The articleaccording to claim 3, wherein the crack mitigating layer comprises asilicon-containing material.
 5. The article according to claim 1,wherein the crack mitigating layer comprises a nano-porous, porous ornon-porous inorganic or hybrid organic-inorganic material.
 6. Thearticle according to claim 1, wherein the substrate is a glass substratethat is chemically strengthened and has a surface compressive stress ofat least 500 MPa and a compressive depth of layer of at least 15 μm. 7.The article according to claim 1, wherein the first film furthercomprises one or more of an average strain-to-failure that is less thanan average strain-to-failure of the substrate and a modulus that isgreater than a modulus of the substrate, and wherein the first film is alayered structure.
 8. The article according to claim 7, wherein thefirst film comprises an anti-reflection (AR) film.
 9. The articleaccording to claim 1, wherein the article is substantially opticallytransparent with an optical transmission haze of 10% or less.
 10. Adisplay device comprising the article of claim 1, wherein the articleserves as a protective cover for the display device.
 11. The article ofclaim 1, wherein the thickness of the crack mitigating layer is fromabout 35 nm to about 80 nm, and the thickness of the substrate is fromabout 300 μm to about 1000 μm.
 12. An article, comprising: a glasssubstrate having a thickness from about 250 μm to about 2000 μm andopposing major surfaces including a first major surface and a secondmajor surface; a crack mitigating layer disposed on and directly incontact with the first major surface of the glass substrate, wherein thecrack mitigating layer comprises (i) a siloxane, a polysiloxane, or anorganically modified silica or silicate and (ii) a thickness from about0.01 μm to about 0.5 μm; and a first film disposed on the crackmitigating layer having a thickness from about 0.01 μm to about 20 μm,wherein the crack mitigating layer has an elastic modulus that is lessthan an elastic modulus of the glass substrate.
 13. The article of claim12, wherein the crack mitigating layer comprises a siloxane.
 14. Thearticle of claim 12, wherein the crack mitigating layer comprises apolysiloxane.
 15. The article of claim 12, wherein the crack mitigatinglayer comprises an organically modified silica or silicate.
 16. Thearticle of claim 12, wherein the thickness of the crack mitigating layeris from about 0.01 μm to less than 0.1 μm.
 17. The article of claim 12,wherein the thickness of the crack mitigating layer is from about 35 nmto about 80 nm, and the thickness of the glass substrate is from about300 μm to about 1000 μm.
 18. An article, comprising: a substrate havinga thickness and opposing major surfaces including a first major surfaceand a second major surface; a crack mitigating layer disposed on anddirectly in contact with the first major surface of the substrate,wherein the crack mitigating layer has a thickness from about 0.01 μm toabout 10 μm; a first film disposed on the crack mitigating layer havinga thickness from about 0.01 μm to about 20 μm; and a further filmdisposed on and in direct contact with the second major surface of thesubstrate having a thickness from about 0.01 μm to about 20 μm, whereinan average strain-to-failure of the substrate is 0.5% or greater, asmeasured with the crack mitigating layer disposed on and directly incontact with the first major surface of the substrate and the first filmdisposed on the crack mitigating layer.
 19. The article according toclaim 18, wherein the further film is a layered structure, and furtherwherein the further film comprises a scratch-resistant layer.
 20. Thearticle according to claim 18, wherein the further film comprises one ormore of SiO₂, Si₃N₄, SiO_(x)N_(y), and combinations thereof.
 21. Thearticle according to claim 18, wherein the article further comprises:one or more additional films disposed on the second major surface of thesubstrate comprising one or more of SiO_(x), SiN_(y), SiO_(x)N_(y), andcombinations thereof.
 22. The article according to claim 18, wherein thefirst film comprises an anti-reflection (AR) film and afingerprint-resistant layer.
 23. The article according to claim 22,wherein the AR film is a layered structure comprising one or more ofSiO₂, TiO₂ and Nb₂O₅.
 24. The article according to claim 18, wherein thecrack mitigating layer has a thickness from about 0.01 μm to less than0.1 μm.
 25. The article according to claim 18, wherein the crackmitigating layer has a modulus that is less than a modulus of the firstfilm and a modulus of the substrate.
 26. The article according to claim18, wherein the crack mitigating layer comprises a porous or non-porouspolymeric material.
 27. The article according to claim 26, wherein thecrack mitigating layer comprises a silicon-containing material.
 28. Thearticle according to claim 18, wherein the crack mitigating layercomprises a nano-porous, porous or non-porous inorganic or hybridorganic-inorganic material.
 29. The article according to claim 18,wherein the substrate is a glass substrate that is chemicallystrengthened and has a surface compressive stress of at least 500 MPaand a compressive depth of layer of at least 15 μm.
 30. The articleaccording to claim 18, wherein the first film further comprises one ormore of an average strain-to-failure that is less than an averagestrain-to-failure of the substrate and a modulus that is greater than amodulus of the substrate.
 31. The article according to claim 18, whereinthe article is substantially optically transparent with an opticaltransmission haze of 10% or less.
 32. A display device comprising thearticle of claim 18, wherein the article serves as a protective coverfor the display device.
 33. The article of claim 18, wherein thethickness of the crack mitigating layer is from about 35 nm to about 80nm, and the thickness of the substrate is from about 300 μm to about1000 μm.
 34. An article, comprising: a glass substrate having athickness and opposing major surfaces including a first major surfaceand a second major surface; a crack mitigating layer disposed on anddirectly in contact with the first major surface of the glass substrate,wherein the crack mitigating layer comprises a silicon-containingpolymeric material and has a thickness from about 0.01 μm to about 0.25μm; a first film disposed on the crack mitigating layer having athickness from about 0.01 μm to about 20 μm; and a further film disposedon and in direct contract with the second major surface of the glasssubstrate having a thickness from about 0.01 μm to about 20 μm, whereinan average strain-to-failure of the glass substrate is 0.5% or greater,as measured with the crack mitigating layer disposed on and directly incontact with the first major surface of the glass substrate and thefirst film disposed on the crack mitigating layer, wherein the firstfilm comprises an anti-reflection (AR) film, the AR film a layeredstructure comprising one or more of SiO₂, TiO₂ and Nb₂O₅, wherein thefurther film is a layered structure that comprises a scratch-resistantlayer and one or more of SiO₂, SiO_(x), SiN_(y), Si₃N₄, SiO_(x)N_(y),and combinations thereof, and further wherein the glass substrate ischemically strengthened and has a surface compressive stress of at least500 MPa and a compressive depth of layer of at least 15 μm.
 35. Thearticle according to claim 34, wherein the crack mitigating layerfurther comprises a modulus that is less than a modulus of the firstfilm and a modulus of the glass substrate and a thickness from about0.01 μm to less than 0.1 μm.
 36. The article according to claim 34,wherein the crack mitigating layer comprises a fracture toughness of 0.5MPa*m^(1/2) or greater.
 37. The article according to claim 34, whereinthe first film further comprises a modulus of at least 25 GPa and ahardness of at least 1.75 GPa.
 38. The article according to claim 34,wherein the article exhibits a reflectance of about 10% or less across avisible wavelength range from 400 nm to 700 nm.
 39. The article of claim34, wherein the thickness of the crack mitigating layer is from about 35nm to about 80 nm, and the thickness of the glass substrate is fromabout 300 μm to about 1000 μm.